public static void setTopologyManager(TopologyManager topologyManager) {
    HostResourceProvider.topologyManager = topologyManager;
  }
Obtain the hostname from the request properties.  The hostname property name may differ
depending on the request type.  For the low level host resource creation calls, it is always
"Hosts/host_name".  For multi host "add host from hostgroup", the hostname property is a top level
property "host_name".

@param properties  request properties

@return the host name for the host request
ambari-server/src/main/java/org/apache/ambari/server/controller/internal/HostResourceProvider.java