YARN-530. Defined Service model strictly, implemented AbstractService for robust subclassing and migrated yarn-common services. Contributed by Steve Loughran.
YARN-117. Migrated rest of YARN to the new service model. Contributed by Steve Louhran.
MAPREDUCE-5298. Moved MapReduce services to YARN-530 stricter lifecycle. Contributed by Steve Loughran.
svn merge --ignore-ancestry -c 1492718 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1492720 13f79535-47bb-0310-9956-ffa450edef68
YARN-746. Renamed Service.register() and Service.unregister() to registerServiceListener() & unregisterServiceListener() respectively. Contributed by Steve Loughran.
svn merge --ignore-ancestry -c 1492780 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1492781 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4902. Merging changes r1492791 from trunk.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1492800 13f79535-47bb-0310-9956-ffa450edef68