HIVE-7643 - ExecMapper static states lead to unpredictable query result. (Chengxiang Li via Brock) [Spark Branch]

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1617772 13f79535-47bb-0310-9956-ffa450edef68
HIVE-7541 : Support union all on Spark (Na Yang via Szehon) [Spark Branch]

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1617790 13f79535-47bb-0310-9956-ffa450edef68