svn merge -c 1507165 from trunk for HADOOP-9773. TestLightWeightCache should not set size limit to zero when esting it.


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1507167 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4979. Merge 1507170 from trunk

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1507173 13f79535-47bb-0310-9956-ffa450edef68