QPID-5715: [Java Broker] Make virtualhosts respect the states ACTIVE and STOPPED

* Changes in virtualhost state are now persisted to store.
* VirtualHostState eliminated.  The PASSIVE state used when a BDB HA Virtualhost is in replica is replaced by UNAVAILABLE.

Work by me and Andrew MacBean <andymacbean@gmail.com>.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1596281 13f79535-47bb-0310-9956-ffa450edef68