QPID-5468: fix handling of delete-if-unused for sending links

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1557279 13f79535-47bb-0310-9956-ffa450edef68
QPID-5469: link should not override a topic policy specifying autodeletion

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1557280 13f79535-47bb-0310-9956-ffa450edef68