HIVE-7917: Re-apply change from HIVE-7158, set hive.exec.reducers.max to a high prime number. (Gopal V, reviewed by Gunther Hagleitner)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/branch-0.14@1630236 13f79535-47bb-0310-9956-ffa450edef68