HIVE-7793 - Enable tests on Spark branch (3) [Sparch Branch] (Chengxiang Li via Brock)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1620660 13f79535-47bb-0310-9956-ffa450edef68
Merge from trunk HIVE-7878 - add -- SORT_BEFORE_DIFF to optimize_nullscan.q test (Venki Korukanti reviewed by Szehon)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1620671 13f79535-47bb-0310-9956-ffa450edef68
HIVE-7844 - optimize_nullscan.q fails due to differences in explain plan [Spark Branch] (Venki Korukanti via Brock)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1620688 13f79535-47bb-0310-9956-ffa450edef68
HIVE-7775 - enable sample8.q [Spark Branch] (Chengxiang Li via Brock)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1620729 13f79535-47bb-0310-9956-ffa450edef68