[EJBCLIENT-120] Hang in AbstractHandleableCloseable.close() when using @Clustered

Extract the logic from cluster context outside EJBClientContext for
uncoupling the operations between EJBClientContext and
ClusterContext. This removes the deadlock when both types
of operations are being invoked through the EJBClientContext.
BZ 6.x https://bugzilla.redhat.com/show_bug.cgi?id=1133980
In other words, if having two locks breaks your code, then this PR is already broken because you have two locks.