Merge -r 1470693:1470694 from trunk to branch-2. Fixes: MAPREDUCE-5146. application classloader may be used too early to load classes. Contributed by Sangjin Lee.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1470696 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/branch-2' into branch-2-gd
Merge remote branch 'origin/branch-2-gd' into fb-YAHOO-271-branch-2-gd