HIVE-6328: Hive script should not overwrite AUX_CLASSPATH with HIVE_AUX_JARS_PATH if the latter is set (reviewed by Prasad)

git-svn-id: https://svn.apache.org/repos/asf/hive/trunk@1563370 13f79535-47bb-0310-9956-ffa450edef68