This plugin worked fine for me with Jenkins 1.451.
I recently upgraded to Jenkins 2.60.2, and everything is working on the new server except monitored remote jobs or External job is not working.
To install the plugin, I extracted the following jar files from the war file and installed them on the remote system as instructed on the plugin wiki.
{{jenkins-core-*.jar }}
{{remoting-*.jar }}
{{ant-1.7.0.jar }}
{{commons-io-1.4jar }}
{{commons-lang-2.4.jar }}
{{jna-posix-*.jar }}
xstream-*.jar
The remote system has java 1.8.
Now when I try to run the cron jobs on the remote system using the jenkins-core.jar, it fails with this trace:

Exception in thread "main" java.lang.NoClassDefFoundError: javax/servlet/ServletContextListener
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:803)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:442)
at java.net.URLClassLoader.access$100(URLClassLoader.java:64)
at java.net.URLClassLoader$1.run(URLClassLoader.java:354)
at java.net.URLClassLoader$1.run(URLClassLoader.java:348)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:347)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at hudson.Main.<clinit>(Main.java:222)
Caused by: java.lang.ClassNotFoundException: javax.servlet.ServletContextListener
at java.net.URLClassLoader$1.run(URLClassLoader.java:359)
at java.net.URLClassLoader$1.run(URLClassLoader.java:348)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:347)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
... 13 more

None of the jar files contain ServletContextListener. From google I learn it is in the servlet api so I found the servlet-api-3.1.0.jar on Oracle's website and tried putting that in the same directory as the other jar files, and setting CLASSPATH, but the same error occurs.
Is this a problem with the plugin or its documentation?
Please suggest for proper solution