QPID-5472: [Java Broker] Connection model object attribute PORT should return the name of the Port

* Added REST system test for the above
* Also addressed review comments from Andrew MacBean (namely, HttpManagement#stop should chain the underlying exception).

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1557683 13f79535-47bb-0310-9956-ffa450edef68