HDFS-5846. Merging change r1581091 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1581092 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-10423. Clarify compatibility policy document for combination of new client and old server. (Chris Nauroth via kasha)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1581117 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-10422. Merging change r1581112 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1581123 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6124. Merging r1581124 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1581137 13f79535-47bb-0310-9956-ffa450edef68
MAPREDUCE-5795. Fixed MRAppMaster to record the correct job-state after it recovers from a commit during a previous attempt. Contributed by Xuan Gong.
svn merge --ignore-ancestry -c 1581180 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1581181 13f79535-47bb-0310-9956-ffa450edef68
svn merge -c 1581183 from trunk for HADOOP-10425. LocalFileSystem.getContentSummary should not count crc files.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1581186 13f79535-47bb-0310-9956-ffa450edef68
YARN-1850. Introduced the ability to optionally disable sending out timeline-events in the TimelineClient. Contributed by Zhijie Shen.
svn merge --ignore-ancestry -c 1581189 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1581190 13f79535-47bb-0310-9956-ffa450edef68