HADOOP-7664. Merging change r1182645 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1610875 13f79535-47bb-0310-9956-ffa450edef68
YARN-2233. Implemented ResourceManager web-services to create, renew and cancel delegation tokens. Contributed by Varun Vasudev.
svn merge --ignore-ancestry -c 1610876 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1610877 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-10673. Merge change r1610879 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1610881 13f79535-47bb-0310-9956-ffa450edef68
YARN-1408 Preemption caused Invalid State Event: ACQUIRED at KILLED and caused a task timeout for 30mins. (Sunil G via mayank)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1610884 13f79535-47bb-0310-9956-ffa450edef68