[WFLY-3711] Re-instate sendClusterRemoved message in VersionOneProtocolChannelReceiver to clean up ClusterContext

This PR does the following:
- reinstates a commented out section of code in the EJBCLient server side code VersionOneProtocolChannelReceiver which sends a protocol message from a server to client when the last member of a cluster has left
- this allows the ClusterContext on the client to be cleaned up 

For details, please see the JIRA issue: https://issues.jboss.org/browse/WFLY-3711