void checkWrappersLoaded() {
    if (!wrappersLoaded) {
      synchronized (this) { // Stages are not used concurrently now, but it won't be performance loss
        if (!wrappersLoaded) {
          loadExecutionCommandWrappers();
        }
      }
    }
  }
Creates object to be persisted in database
@return StageEntity
ambari-server/src/main/java/org/apache/ambari/server/actionmanager/Stage.java