[Back-port to 4.2.x] ResourceBundleWorkflowEventListener fail in case of multi HST webapp setup

Reproducible by starting up the testsuite

[INFO] [talledLocalContainer] 2017-04-10 16:46:23,376 ERROR [pool-4-thread-1] [org.hippoecm.repository.events.BroadcastModule.getPersistedHippoEventsServiceRegistrations():193] Invalid PersistedWorkflowEventsService registration: listener org.hippoecm.hst.resourcebundle.internal.ResourceBundleWorkflowEventListener subscribes to channel [org.hippoecm.hst.resourcebundle.internal.ResourceBundleWorkflowEventListener] which alreadyhas been subscribed to by: org.hippoecm.hst.resourcebundle.internal.ResourceBundleWorkflowEventListener. Only the first listener will receive events.