Merge r1580154 from trunk. YARN-1776. Fixed DelegationToken renewal to survive RM failover. Contributed by Zhijie Shen

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1580156 13f79535-47bb-0310-9956-ffa450edef68
YARN-1577. Made UnmanagedAMLauncher do launchAM after the attempt reaches the LAUNCHED state. Contributed by Jian He.
svn merge --ignore-ancestry -c 1580164 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1580165 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-10191. Merging change r1580170 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1580171 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6140. Merging change r1580173 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1580174 13f79535-47bb-0310-9956-ffa450edef68