HDFS-6072. Clean up dead code of FSImage. Contributed by Haohui Mai.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1576513 13f79535-47bb-0310-9956-ffa450edef68
YARN-1821. NPE on registerNodeManager if the request has containers for UnmanagedAMs (kasha)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1576525 13f79535-47bb-0310-9956-ffa450edef68