YARN-495. Changed NM reboot behaviour to be a simple resync - kill all containers  and re-register with RM. Contributed by Jian He.
svn merge --ignore-ancestry -c 1466752 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1466753 13f79535-47bb-0310-9956-ffa450edef68