ISPN-4792 RemoteClusterListener still invokes filter/converter

* Added post filter so only post events are passed to cluster listeners

https://issues.jboss.org/browse/ISPN-4792
Hrmm yeah I was debating about this.  I always struggle between having a static instance variable like that when it isn't used, but obviously helps when more than 1 cluster listener is installed (albeit a small amount)