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.

merged from trunk r1464938


git-svn-id: https://svn.apache.org/repos/asf/qpid/branches/0.22@1469856 13f79535-47bb-0310-9956-ffa450edef68