HIVE-8921 : Investigate test failure on auto_join2.q [Spark Branch] (Chao Sun via Szehon)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1640858 13f79535-47bb-0310-9956-ffa450edef68
HIVE-8908 : Investigate test failure on join34.q [Spark Branch] (Chao Sun via Szehon)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1640859 13f79535-47bb-0310-9956-ffa450edef68
HIVE-8868: SparkSession and SparkClient mapping[Spark Branch] (Rui via Xuefu)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1640916 13f79535-47bb-0310-9956-ffa450edef68
HIVE-8756: numRows and rawDataSize are not collected by the Spark stats [Spark Branch] (Na via Xuefu)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1640934 13f79535-47bb-0310-9956-ffa450edef68
HIVE-8942 : Investigate test failure on skewjoin.q [Spark Branch] (Chao Sun via Szehon)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1641023 13f79535-47bb-0310-9956-ffa450edef68
Merge remote-tracking branch 'upstream/spark' into spark