QPID-4849 The previous code was assuming that "CN" was the first entry
in the name string. Changed the code to first find "CN" and then extract
from there. testMultipleCertsInSingleStore verifies this change.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1483079 13f79535-47bb-0310-9956-ffa450edef68