HDFS-4763 Add script changes/utility for starting NFS gateway

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1511519 13f79535-47bb-0310-9956-ffa450edef68
fix hadoop-hdfs/CHANGES.txt for HDFS-4763

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1511521 13f79535-47bb-0310-9956-ffa450edef68