Backporting AMBARI-1794, AMBARI-1795, and AMBARI-1815 to 1.2 branch. (yusaku)

git-svn-id: https://svn.apache.org/repos/asf/incubator/ambari/branches/branch-1.2@1464877 13f79535-47bb-0310-9956-ffa450edef68