Reject incoming requests on shutdown

[damnever]

Checklist

• [ ] Tests updated
• [ ] Documentation added
• [x] CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[damnever]

We only reject incoming requests for v1 chunk storage, I think we should do it for v2 block storage as well.

[danielblando]

@damnever Do you have any use case or example of this happening? The only think I could think is maybe concurrence issue, because we do have a check on these on

https://github.com/cortexproject/cortex/blob/96d1d7cdd725ab6066e33728813685674810f72a/pkg/ingester/ingester.go#L496-L499

And the service will be at Stopping when it start to shutdown even before running the stopping function. https://github.com/cortexproject/cortex/blob/master/pkg/util/services/basic_service.go#L195

[alanprot]

I think i did this on the refactor when removing chunks storage.