func (engine *DockerTaskEngine) isTaskManaged(arn string) bool {
	engine.tasksLock.RLock()
	defer engine.tasksLock.RUnlock()
	_, ok := engine.managedTasks[arn]
	return ok
}
func (engine *DockerTaskEngine) isTaskManaged(arn string) bool {
	engine.tasksLock.RLock()
	defer engine.tasksLock.RUnlock()
	_, ok := engine.managedTasks[arn]
	return ok
}
// isTaskManaged checks if task for the corresponding arn is present