* Poll the substream validation before polling `Notifications`
In tests, it can happen that `Notifications` doesn't produce any events
which causes `poll()` to return `Poll::Pending` and the substream
validation futures won't get polled.
Poll the futures before calling `Notifications` so results for substream
validations are received even if `Notifications` is not producing any
events.
* Remove `pending_messages`
* Remove unused import
Aaro Altonen
818976d98e