QPID-4623: Fixed unknown semantics of "between" comparison

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1457058 13f79535-47bb-0310-9956-ffa450edef68
QPID-4623: Fixed the unit test for unknown values

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1457062 13f79535-47bb-0310-9956-ffa450edef68