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 remote branch 'origin/branch-2' into branch-2-gd
Merge remote branch 'origin/branch-2-gd' into fb-HADOOP-9016-branch-2-gd