Do not disconnect peers due to missing subnet overlap if we ourselves are not subscribed to anything yet #765
Description
If we have not subscribed to any subnets yet, e.g. because we are syncing, or because the heartbeat will always disconnect all peers.
This is not desirable. We should not perform this check while we are not subscribed to anything yet in order to not lose peers that might be relevant later.
This is nice for e.g. local devnets, but should be also beneficial for other scenarios such as peering of a private cluster which is in the process of being set up.