QPID-6290: [Java Broker] Management UI - refactor add VHN/VH to remove type based conditional logic

* Also removed now defunct Broker attributes #supportedVirtualHostNodeTypes and #supportedVirtualHostTypes

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1648245 13f79535-47bb-0310-9956-ffa450edef68