AMBARI-1456. Cannot proceed after bootstrapping in some cases due to a run-time error while running host checks. (yusaku)

git-svn-id: https://svn.apache.org/repos/asf/incubator/ambari/trunk@1448431 13f79535-47bb-0310-9956-ffa450edef68
AMBARI-1441.Validation for username used in service configs is broken. (yusaku)

git-svn-id: https://svn.apache.org/repos/asf/incubator/ambari/trunk@1448435 13f79535-47bb-0310-9956-ffa450edef68