Enable Infinispan standalone's Channel to be plugged with MessageListeners

Investigate what would need doing to enable Infinispan to receive a JGroups' Channel or ChannelFactory that allows users to add their own message listeners when such clients want to be sending rpcs around.

Brian will be using a solution like this for the AS case but since AS is owner of the Channel, this is relatively easy for it assuming that JGroups has the right API for it.