You downgraded to 2.1 and the issue goes away?

Downgraded resolved this for me.

Strange, I don't even see token macro in the stack trace. I'm not sure how to debug this as I don't have docker in my environment.

It's definitely a strange one. I found I could reproduce it by adding a "Docker Cloud" config, giving a valid URL and then just testing the connection. No idea if that makes the repro easier or not.

FWIW, I didn't see anything suspicious when looking at the changes between 2.1 and 2.2.

I'm wondering if a new dependency in token macro for jsonpath is causing a problem. I'll try out what you mentioned for repro.

Downgrading did solve the issue.  I'm definitely willing to help troubleshoot in any way I can.

Here's a little more meaningful exception:

WARNING: Error while serving http://192.168.99.100/cicada/descriptorByName/com.nirima.jenkins.plugins.docker.DockerCloud/testConnection
java.lang.reflect.InvocationTargetException
    at org.kohsuke.stapler.Function$MethodFunction.invoke(Function.java:347)
    at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:184)
    at org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:117)
    at org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:129)
    at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:58)
    at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:715)
    at org.kohsuke.stapler.Stapler.invoke(Stapler.java:845)
    at org.kohsuke.stapler.MetaClass$5.doDispatch(MetaClass.java:248)
    at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:58)
    at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:715)
    at org.kohsuke.stapler.Stapler.invoke(Stapler.java:845)
    at org.kohsuke.stapler.Stapler.invoke(Stapler.java:649)
    at org.kohsuke.stapler.Stapler.service(Stapler.java:238)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:812)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1669)
    at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:135)
    at org.jenkinsci.plugins.ssegateway.Endpoint$SSEListenChannelFilter.doFilter(Endpoint.java:225)
    at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
    at io.jenkins.blueocean.auth.jwt.impl.JwtAuthenticationFilter.doFilter(JwtAuthenticationFilter.java:51)
    at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
    at com.smartcodeltd.jenkinsci.plugin.assetbundler.filters.LessCSS.doFilter(LessCSS.java:47)
    at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
    at io.jenkins.blueocean.ResourceCacheControl.doFilter(ResourceCacheControl.java:134)
    at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
    at hudson.plugins.greenballs.GreenBallFilter.doFilter(GreenBallFilter.java:59)
    at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
    at hudson.plugins.audit_trail.AuditTrailFilter.doFilter(AuditTrailFilter.java:95)
    at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
    at jenkins.metrics.impl.MetricsFilter.doFilter(MetricsFilter.java:125)
    at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:132)
    at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:138)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
    at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:49)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
    at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
    at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:90)
    at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:171)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
    at org.kohsuke.stapler.compression.CompressionFilter.doFilter(CompressionFilter.java:49)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
    at hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:82)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
    at org.kohsuke.stapler.DiagnosticThreadNameFilter.doFilter(DiagnosticThreadNameFilter.java:30)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:585)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
    at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:553)
    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:223)
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1127)
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:515)
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1061)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
    at org.eclipse.jetty.server.Server.handle(Server.java:499)
    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:311)
    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:257)
    at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:544)
    at winstone.BoundedExecutorService$1.run(BoundedExecutorService.java:77)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NoSuchMethodError: com.fasterxml.jackson.databind.ObjectReader.forType(Lcom/fasterxml/jackson/databind/JavaType;)Lcom/fasterxml/jackson/databind/ObjectReader;
    at com.fasterxml.jackson.jaxrs.base.ProviderBase.readFrom(ProviderBase.java:799)
    at org.glassfish.jersey.message.internal.ReaderInterceptorExecutor$TerminalReaderInterceptor.invokeReadFrom(ReaderInterceptorExecutor.java:256)
    at org.glassfish.jersey.message.internal.ReaderInterceptorExecutor$TerminalReaderInterceptor.aroundReadFrom(ReaderInterceptorExecutor.java:235)
    at org.glassfish.jersey.message.internal.ReaderInterceptorExecutor.proceed(ReaderInterceptorExecutor.java:155)
    at org.glassfish.jersey.message.internal.MessageBodyFactory.readFrom(MessageBodyFactory.java:1085)
    at org.glassfish.jersey.message.internal.InboundMessageContext.readEntity(InboundMessageContext.java:874)
    at org.glassfish.jersey.message.internal.InboundMessageContext.readEntity(InboundMessageContext.java:808)
    at org.glassfish.jersey.client.ClientResponse.readEntity(ClientResponse.java:326)
    at org.glassfish.jersey.client.JerseyInvocation.translate(JerseyInvocation.java:806)
    at org.glassfish.jersey.client.JerseyInvocation.access$700(JerseyInvocation.java:92)
    at org.glassfish.jersey.client.JerseyInvocation$2.call(JerseyInvocation.java:701)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:228)
    at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:444)
    at org.glassfish.jersey.client.JerseyInvocation.invoke(JerseyInvocation.java:697)
    at org.glassfish.jersey.client.JerseyInvocation$Builder.method(JerseyInvocation.java:420)
    at org.glassfish.jersey.client.JerseyInvocation$Builder.get(JerseyInvocation.java:316)
    at com.github.dockerjava.jaxrs.VersionCmdExec.execute(VersionCmdExec.java:26)
    at com.github.dockerjava.jaxrs.VersionCmdExec.execute(VersionCmdExec.java:13)
    at com.github.dockerjava.jaxrs.AbstrSyncDockerCmdExec.exec(AbstrSyncDockerCmdExec.java:23)
    at com.github.dockerjava.core.command.AbstrDockerCmd.exec(AbstrDockerCmd.java:35)
    at com.nirima.jenkins.plugins.docker.DockerCloud$DescriptorImpl.doTestConnection(DockerCloud.java:698)
    at java.lang.invoke.MethodHandle.invokeWithArguments(MethodHandle.java:627)
    at org.kohsuke.stapler.Function$MethodFunction.invoke(Function.java:343)
    ... 62 more

Ok, it looks like the jsonpath library does have a dependency (optional) on com.fasterxml.jackson.core, so there is probably a version mismatch issue that is causing this problem. I'll add an exclusion to the pom and upload an hpi for you to try (if you are willing). If it works, I can do a quick update release.