HDFS-5228. The RemoteIterator returned by DistributedFileSystem.listFiles may throw NullPointerException.  Contributed by szetszwo and cnauroth


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1525828 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd
Merge remote branch 'origin/trunk-gd' into fb-HDFS-4312-trunk-gd