@Transactional
  void deleteConfigGroupHostMapping(Long hostId) throws AmbariException {
    // Remove Config group mapping
    for (Cluster cluster : getClustersByName().values()) {
      for (ConfigGroup configGroup : cluster.getConfigGroups().values()) {
        configGroup.removeHost(hostId);
      }
    }
  }
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