@Override
          public Long apply(Stage stage) {
            return stage.getRequestId();
          }
publish event to load {@link TaskStatusListener#activeTasksMap} {@link TaskStatusListener#activeStageMap}
and {@link TaskStatusListener#activeRequestMap} for all running request once during server startup.
This is required as some tasks may have been in progress when server was last stopped
@param stages list of stages
ambari-server/src/main/java/org/apache/ambari/server/actionmanager/ActionScheduler.java