HADOOP-10890: Merging r1612917 from branch-2 to branch-2.5.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.5@1612918 13f79535-47bb-0310-9956-ffa450edef68
Merge from trunk. HDFS-6422. getfattr in CLI doesn't throw exception or return non-0 return code when xattr doesn't exist. (Charles Lamb via umamahesh)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.5@1612924 13f79535-47bb-0310-9956-ffa450edef68