HDFS-4932. Merging change r1497141 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1497143 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-9673. NetworkTopology: When a node cannot be added, print out its location for diagnostic purposes

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1497180 13f79535-47bb-0310-9956-ffa450edef68