Merge -c 1493445 from trunk to branch-2 to fix MAPREDUCE-5192. Allow for alternate resolutions of TaskCompletionEvents. Contributed by Chris Douglas.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1493446 13f79535-47bb-0310-9956-ffa450edef68
YARN-693. Modified RM to send NMTokens on allocate call so that AMs can then use them for authentication with NMs. Contributed by Omkar Vinit Joshi.
svn merge --ignore-ancestry -c 1493448 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1493449 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-9632. Merging change r1493451 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1493453 13f79535-47bb-0310-9956-ffa450edef68