HDFS-6100. Merge r1579301 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1579303 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-10221. Merging r1579382 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1579383 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-10221. Merging r1579387 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1579388 13f79535-47bb-0310-9956-ffa450edef68
svn merge -c 1579396 from trunk for HDFS-6123. Do not log stack trace for ReplicaAlreadyExistsException and SocketTimeoutException.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1579397 13f79535-47bb-0310-9956-ffa450edef68