[master] Fix for EJBCLIENT-70

The commit here fixes the issue reported in https://issues.jboss.org/browse/EJBCLIENT-70 where the proxies returned via calls to getEJBHome() and the (entity bean) finder methods could potentially lose the EJB client context identifier associated with the original proxy on which the call happened. The fix is similar to what we did for https://issues.jboss.org/browse/EJBCLIENT-51.