YARN-2054. Better defaults for YARN ZK configs for retries and retry-inteval when HA is enabled. (kasha)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1598632 13f79535-47bb-0310-9956-ffa450edef68
YARN-2010. Document yarn.resourcemanager.zk-auth and its scope. (Robert Kanter via kasha)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1598637 13f79535-47bb-0310-9956-ffa450edef68