HORNETQ-1047 - Fail-over after fail-back doesn't work in JBoss AS

I added a callback on the JMSServerManagerImpl so that when HornetQServerImpl fails-back it can clean up all the JMS admin objects (including their JNDI entries).  I also do no clear the "cachedCommands" so that they can be executed again when fail-over occurs again.  Otherwise the JMS admin objects would not get re-created and bound back into JNDI properly.