HIVE-4620 MR temp directory conflicts in case of parallel execution mode (Prasad Mujumdar via Navis)

git-svn-id: https://svn.apache.org/repos/asf/hive/trunk@1489226 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd
Merge remote branch 'origin/trunk-gd' into fb-YAHOO-321-trunk-gd