HDFS-4340. Merge r1448502 from trunk

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1471698 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4434. Merge r1469644 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1471703 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4739. NN can miscalculate the number of extra edit log segments to retain. Contributed by Aaron T. Myers.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1471773 13f79535-47bb-0310-9956-ffa450edef68
Update CHANGES.txt for HDFS-4739.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1471775 13f79535-47bb-0310-9956-ffa450edef68
Merge -c 1471796 from trunk to branch-2 to fix MAPREDUCE-5166. Fix ConcurrentModificationException due to insufficient synchronization on updates to task Counters. Contributed by Sandy Ryza.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1471797 13f79535-47bb-0310-9956-ffa450edef68
merge YARN-579 from trunk. Stop setting the Application Token in the AppMaster env, in favour of the copy present in the container token field. Contributed by Vinod Kumar Vavilapalli.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1471815 13f79535-47bb-0310-9956-ffa450edef68
merge MAPREDUCE-5181 from trunk. RMCommunicator should not use AMToken from the env. Contributed by Vinod Kumar Vavilapalli. 


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1471817 13f79535-47bb-0310-9956-ffa450edef68