High CPU usage on idle, disable dashboard and metric collection

Hello,

I was wondering if there's a way to disable metric collection shown on the admin dashboard ?

My original issue was I found dask has high CPU usage on idle (~10% on per worker). I found [this issue](https://github.com/dask/distributed/issues/2156#issuecomment-503735503) and set the following config, which eventually brought down the high CPU to around 2-4%

```
import dask
from dask.distributed import Client

dask.config.set({
'distributed.admin.tick.interval': '1000ms',
'distributed.worker.profile.interval': '1000ms'
})
```

Then I tried to disable the dashboard itself by setting `dashboard_address` to None, when I start the client. I notice no change in CPU usage. Why does dask still continue to collect metrics (If it is) even after setting dashboard to None ?

Thanks!