HDFS-4594. Merging change r1516008 from branch-2 to branch-2.1-beta.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1-beta@1516224 13f79535-47bb-0310-9956-ffa450edef68
MAPREDUCE-5466. Changed MR AM to not promote history files of intermediate AMs in case they are exiting because of errors and thus help history-server pick up the right history file for the last successful AM. Contributed by Jian He.
svn merge --ignore-ancestry -c 1516238 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1-beta@1516241 13f79535-47bb-0310-9956-ffa450edef68