PIG-3842: Pig on tez job hangs when AM has a failure and Multiquery fixes (rohini)

git-svn-id: https://svn.apache.org/repos/asf/pig/branches/tez@1586670 13f79535-47bb-0310-9956-ffa450edef68
PIG-3875: Fix MergeJoin_8 failure

git-svn-id: https://svn.apache.org/repos/asf/pig/branches/tez@1586742 13f79535-47bb-0310-9956-ffa450edef68