OPENJPA-1979: Regression for non-standard joins with constant column values - back ported to 2.2.1.x Pinaki Poddar's trunk changes.

git-svn-id: https://svn.apache.org/repos/asf/openjpa/branches/2.2.1.x@1484322 13f79535-47bb-0310-9956-ffa450edef68