Merge -r 1448614:1448615 from trunk to branch. Fixes: MAPREDUCE-4951. Container preemption interpreted as task failure. Contributed by Sandy Ryza.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1448618 13f79535-47bb-0310-9956-ffa450edef68