HDFS-4261. Fix bugs in Balaner causing infinite loop and TestBalancerWithNodeGroup timeing out.  Contributed by Junping Du


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1430917 13f79535-47bb-0310-9956-ffa450edef68
MAPREDUCE-1700. User supplied dependencies may conflict with MapReduce system JARs.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1430929 13f79535-47bb-0310-9956-ffa450edef68