Clean up EDL controller

https://github.com/PaddlePaddle/cloud/blob/dcebcdf820d4a7aa13e815e75d3a17f705794ec1/go/cmd/autoscaler/autoscaler.go#L61-L63

```go
	ctx, cancelFunc := context.WithCancel(context.Background())
	defer cancelFunc()
	controller.Run(ctx)
```

should be

```go
controller.Run(context.Background())
```