agent/engine/docker_task_engine.go
func (engine *DockerTaskEngine) GetTaskByArn(arn string) (*apitask.Task, bool) {
	return engine.state.TaskByArn(arn)
}
func (engine *DockerTaskEngine) GetTaskByArn(arn string) (*apitask.Task, bool) {
	return engine.state.TaskByArn(arn)
}
// GetTaskByArn returns the task identified by that ARN