svn merge -c 1583018 from trunk for HDFS-6166. Change Balancer socket read timeout to 20 minutes and add 10 seconds delay after error.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.4@1583020 13f79535-47bb-0310-9956-ffa450edef68