agent/engine/dockerstate/docker_task_engine_state.go
func (state *DockerTaskEngineState) TaskByArn(arn string) (*apitask.Task, bool) {
	state.lock.RLock()
	defer state.lock.RUnlock()

	return state.taskByArn(arn)
}
func (state *DockerTaskEngineState) TaskByArn(arn string) (*apitask.Task, bool) {
	state.lock.RLock()
	defer state.lock.RUnlock()

	return state.taskByArn(arn)
}
// TaskByArn returns a task for a given ARN