HIVE-8276: Separate shuffle from ReduceTran and so create ShuffleTran [Spark Branch] (Chao via Xuefu)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1631140 13f79535-47bb-0310-9956-ffa450edef68
Merge remote-tracking branch 'upstream/spark' into spark