HADOOP-9638. Merging change r1492314 from branch-2 to branch-2.1-beta.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1-beta@1492322 13f79535-47bb-0310-9956-ffa450edef68
MAPREDUCE-5304. mapreduce.Job killTask/failTask/getTaskCompletionEvents methods have incompatible signature changes. (kkambatl via tucu)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1-beta@1492363 13f79535-47bb-0310-9956-ffa450edef68