HDFS-5585. Provide admin commands for data node upgrade. Contributed by Kihwal Lee.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-5535@1568523 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5585. Provide admin commands for data node upgrade. Contributed by Kihwal Lee. (missing file)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-5535@1568524 13f79535-47bb-0310-9956-ffa450edef68