HDFS-6772: Merging r1616680 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1616681 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-10771. Addendum, default realm correction to common test krb5.conf file. (tucu)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1616682 13f79535-47bb-0310-9956-ffa450edef68