HADOOP-8545. Fixed merge to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1527052 13f79535-47bb-0310-9956-ffa450edef68
Merge -c 1527048 from trunk to branch-2 to fix MAPREDUCE-5529. Fix compat with hadoop-1 in mapred.TotalOrderPartitioner by re-introducing (get,set)PartitionFile which takes in JobConf. Contributed by Robert Kanter.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1527054 13f79535-47bb-0310-9956-ffa450edef68