QPID-4676: set the certificate alias to use for the client to ensure the test behaviour is deterministic, the keystore has 2 certs and different JVMs can select differently as to which is used by default, resulting in test failure on certain platforms.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1464938 13f79535-47bb-0310-9956-ffa450edef68