YARN-1962. Changed Timeline Service client configuration to be off by default given the non-readiness of the feature yet. Contributed by Mohammad Kamrul Islam.
svn merge --ignore-ancestry -c 1593750 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.4@1593752 13f79535-47bb-0310-9956-ffa450edef68