MAPREDUCE-4930. Backport MAPREDUCE-4678 and MAPREDUCE-4925 to branch-1. Contributed by Karthik Kambatla and Chris McConnell. (harsh)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1@1433428 13f79535-47bb-0310-9956-ffa450edef68