HIVE-8995: Find thread leak in RSC Tests [Spark Branch] (Rui via Xuefu)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1642894 13f79535-47bb-0310-9956-ffa450edef68
HIVE-8970: Enable map join optimization only when hive.auto.convert.join is true [Spark Branch] (Chao via Xuefu)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1642997 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'upstream/spark' into spark