0.4.1 relays should list Padding=2
Somehow we accidentally merged the protover for padding support while doing the incremental merge thing, and 0.4.0 relays are advertising padding that they don't support. This is mostly harmless, because the negotiation will not succeed and then clients will stop, but it will result in those clients emitting a "Middle node did not accept our padding request" protocol warn/info message.
We should just remove this protover field from 0.4.0.x.
At the weekly meeting last week, we decided that we can't remove a protover once it's been released. Instead, we will:
- make 0.4.1 and later relays declare Padding=2 (pre-0.4.1 stable)
- make 0.4.1 and later clients require Padding=2 (padding is not on by default, so we can do this at any time)
Edited to simplify: we don't need to preserve compatibility with alphas.