QPID-5650: Move attribute names into upgrader constants

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1635183 13f79535-47bb-0310-9956-ffa450edef68
QPID-6196: Add synchronization on CO registration to avoid creation of objects with duplicate names and ids

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1635184 13f79535-47bb-0310-9956-ffa450edef68