@Override
  public void unmapHostFromCluster(String hostname, String clusterName) throws AmbariException {
    final Cluster cluster = getCluster(clusterName);
    Host host = getHost(hostname);

    unmapHostFromClusters(host, Sets.newHashSet(cluster));

    cluster.refresh();
  }
Attempts to map the host to the cluster via clusterhostmapping table if not already present, and add a host_version
record for the cluster's currently applied (stack, version) if not already present.
@param hostname Host name
@param clusterName Cluster name
@throws AmbariException May throw a DuplicateResourceException.
ambari-server/src/main/java/org/apache/ambari/server/state/cluster/ClustersImpl.java