OPENJPA-2425: SELECT fields with @ExternalValues defined returns datastore values instead of unmapped fields - applied Albert Lee's patch to 2.2.1.x.

git-svn-id: https://svn.apache.org/repos/asf/openjpa/branches/2.2.1.x@1530347 13f79535-47bb-0310-9956-ffa450edef68