code: @Override
      public boolean cancel(String appName, String id, boolean isReplication) {
          return internalCancel(appName, id, isReplication);
      }
docs: Cancels the registration of an instance.
  
  <p>
  This is normally invoked by a client when it shuts down informing the
  server to remove the instance from traffic.
  </p>
  
  @param appName the application name of the application.
  @param id the unique identifier of the instance.
  @param isReplication true if this is a replication event from other nodes, false
  otherwise.
  @return true if the instance was removed from the {@link AbstractInstanceRegistry} successfully, false otherwise.