HDFS-5399. Revisit SafeModeException and corresponding retry policies. Contributed by Haohui Mai.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1564628 13f79535-47bb-0310-9956-ffa450edef68
Correct CHANGES.txt entry for HDFS-5399 (contributed by Jing, not Haohui)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1564631 13f79535-47bb-0310-9956-ffa450edef68
YARN-1461. Added tags for YARN applications and changed RM to handle them. Contributed by Karthik Kambatla.
svn merge --ignore-ancestry -c 1564633 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1564634 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-10273. Merging r1564638 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1564639 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5709. Improve NameNode upgrade with existing reserved paths and path components. Contributed by Andrew Wang.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1564647 13f79535-47bb-0310-9956-ffa450edef68