OPENJPA-2492.  Committing a variation of the patch as provided by Romain Manni-Bucau.  This patch clears up the ConcurrentHashMap issues relating to the KeySetView return type.  This patch also adds a couple of asserts to an existing testcase to verify the results.

git-svn-id: https://svn.apache.org/repos/asf/openjpa/trunk@1589187 13f79535-47bb-0310-9956-ffa450edef68