QPID-4671: [Java Broker] Fix NPE occuring in FanoutExchange#isBound(... AMQQueue) when queue parameter is null

merged from trunk r1462162


git-svn-id: https://svn.apache.org/repos/asf/qpid/branches/0.22@1462778 13f79535-47bb-0310-9956-ffa450edef68