AMBARI-2309. Revert Hadoop2 check for empty 'dfs.hosts' and 'dfs.hosts.exclude' properties. (srimanth)

git-svn-id: https://svn.apache.org/repos/asf/incubator/ambari/branches/branch-1.4.0@1490485 13f79535-47bb-0310-9956-ffa450edef68