MAPREDUCE-5476. Changed MR AM recovery code to cleanup staging-directory only after unregistering from the RM. Contributed by Jian He.
svn merge --ignore-ancestry -c 1516660 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1516662 13f79535-47bb-0310-9956-ffa450edef68