HIVE-6222 Make Vector Group By operator abandon grouping if too many distinct keys (reviewed by Jitendra)

git-svn-id: https://svn.apache.org/repos/asf/hive/trunk@1580179 13f79535-47bb-0310-9956-ffa450edef68
HIVE-6472: JDBC cancel will not work with current HiveServer2 (Vaibhav Gumashta via Prasad Mujumdar)

git-svn-id: https://svn.apache.org/repos/asf/hive/trunk@1580264 13f79535-47bb-0310-9956-ffa450edef68