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/trunk@1470694 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4725: shutdown MiniDFSCluster in TestDistributedFileSystem
HDFS-4725: close MiniDFSCluster in TestQuota
Merge branch 'trunk' into HDFS-4725