Merge r1574997 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1574999 13f79535-47bb-0310-9956-ffa450edef68
HDFS-6059. TestBlockReaderLocal fails if native library not available (ajisakaa via cmccabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1575000 13f79535-47bb-0310-9956-ffa450edef68