HIVE-8017: Use HiveKey instead of BytesWritable as key type of the pair RDD [Spark Branch] Rui Li via Xuefu

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1624584 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'upstream/spark' into spark