code: protected Map<String, Object> unsetConfiguration(ServiceReference<SecurityConfiguration> ref) {
          configs.removeReference((String) ref.getProperty(KEY_ID), ref);
          return getServiceProperties();
      }
docs: Method will be called for each SecurityConfiguration that is unregistered
  in the OSGi service registry. We must remove this instance from our
  internal map.
  
  @param ref Reference to an unregistered SecurityConfiguration