Refactor and expand the multi-threaded query tests to cover SELECT as well.  Determine that I can indeed reproduce the failures intermittently for JENA-399.  The tests that fail are currently @Ignore'd until a workaround can be made

git-svn-id: https://svn.apache.org/repos/asf/jena/trunk@1448875 13f79535-47bb-0310-9956-ffa450edef68