[JENKINS-38370] - ExtensionPoints may be used on agents (#2605)

We have to do it, because some extension points are being executed on slaves (e.g. https://github.com/jenkinsci/cygwin-process-killer-plugin/blob/master/src/main/java/com/synopsys/arc/jenkinsci/plugins/cygwinprocesskiller/CygwinProcessKiller.java - ProcessKiller EP gets propagated).