Failed to count the # of live instances on Kubernetes
io.fabric8.kubernetes.client.KubernetesClientException: Failure executing: GET at: https://kubernetes.default/api/v1/namespaces/prod-jenkins/pods?labelSelector=jenkins%3Dslave%2Cjenkins%2Flabel%3Dlinux_alpine_openjdk_jdk8_4g_. Message: unable to parse requirement: invalid label value: "linux_alpine_openjdk_jdk8_4g_": at key: "jenkins/label": a valid label must be an empty string or consist of alphanumeric characters, '-', '_' or '.', and must start and end with an alphanumeric character (e.g. 'MyValue', or 'my_value', or '12345', regex used for validation is '(([A-Za-z0-9][-A-Za-z0-9_.]*)?[A-Za-z0-9])?'). Received status: Status(apiVersion=v1, code=400, details=null, kind=Status, message=unable to parse requirement: invalid label value: "linux_alpine_openjdk_jdk8_4g_": at key: "jenkins/label": a valid label must be an empty string or consist of alphanumeric characters, '-', '_' or '.', and must start and end with an alphanumeric character (e.g. 'MyValue', or 'my_value', or '12345', regex used for validation is '(([A-Za-z0-9][-A-Za-z0-9_.]*)?[A-Za-z0-9])?'), metadata=ListMeta(_continue=null, remainingItemCount=null, resourceVersion=null, selfLink=null, additionalProperties={}), reason=BadRequest, status=Failure, additionalProperties={}).
 at io.fabric8.kubernetes.client.dsl.base.OperationSupport.requestFailure(OperationSupport.java:510)
 at io.fabric8.kubernetes.client.dsl.base.OperationSupport.assertResponseCode(OperationSupport.java:449)
 at io.fabric8.kubernetes.client.dsl.base.OperationSupport.handleResponse(OperationSupport.java:413)
 at io.fabric8.kubernetes.client.dsl.base.OperationSupport.handleResponse(OperationSupport.java:372)
 at io.fabric8.kubernetes.client.dsl.base.OperationSupport.handleResponse(OperationSupport.java:354)
 at io.fabric8.kubernetes.client.dsl.base.BaseOperation.listRequestHelper(BaseOperation.java:153)
 at io.fabric8.kubernetes.client.dsl.base.BaseOperation.list(BaseOperation.java:620)
 at io.fabric8.kubernetes.client.dsl.base.BaseOperation.list(BaseOperation.java:69)
 at org.csanchez.jenkins.plugins.kubernetes.KubernetesCloud.getActiveSlavePods(KubernetesCloud.java:608)
 at org.csanchez.jenkins.plugins.kubernetes.KubernetesCloud.addProvisionedSlave(KubernetesCloud.java:593)
 at org.csanchez.jenkins.plugins.kubernetes.KubernetesCloud.provision(KubernetesCloud.java:535)
 at hudson.slaves.NodeProvisioner$StandardStrategyImpl.apply(NodeProvisioner.java:725)
 at hudson.slaves.NodeProvisioner.update(NodeProvisioner.java:332)
 at hudson.slaves.NodeProvisioner.access$900(NodeProvisioner.java:63)
 at hudson.slaves.NodeProvisioner$NodeProvisionerInvoker.doRun(NodeProvisioner.java:819)
 at hudson.triggers.SafeTimerTask.run(SafeTimerTask.java:70)
 at jenkins.security.ImpersonatingScheduledExecutorService$1.run(ImpersonatingScheduledExecutorService.java:58)
 at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
 at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
 at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
 at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
 at java.lang.Thread.run(Thread.java:748)