Add test of a node using a rolled-back cert

[eddyashton]

Noted and mitigated around #7057.

A node updates the cert it will put into signatures and use for node-to-node channels on a local hook. That means it might be rolled back. There's a comment saying that's safe, because this cert is only modified when a node is added, so a rollback means the node is removed.

That's not true!

The cert is also updated on cert refresh. This could also be rolled back, and result in the node using a cert which has not been written to the ledger.

[achamayou]

I think this is a dupe of #3250, but good point about the refresh.