HDFS-5320. Add datanode caching metrics. Contributed by Andrew Wang.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1540796 13f79535-47bb-0310-9956-ffa450edef68
MAPREDUCE-5186. mapreduce.job.max.split.locations causes some splits created by CombineFileInputFormat to fail. Contributed by Robert Parker and Jason Lowe


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1540813 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5467. Remove tab characters in hdfs-default.xml. Contributed by Shinichi Yamashita.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1540816 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd
Merge remote branch 'origin/trunk-gd' into fb-HDFS-4311-INVESTIGATION-trunk-gd