connectd is going to end up using this do demux; make it fast and complete.
Fixing this reveals a problem in openingd: it now extracts the channel_id
from funding_signed (which is where we transition off the temporary), and
gets upset. So fix that.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
> If the peer's revocation basepoint is unknown (e.g. `open_channel2`),
> a temporary `channel_id` should be found by using a zeroed out basepoint
> for the unknown peer.
v2 of channel open uses the channel revocation basepoints to calculate
the channel_id, instead of the funding_txid + outnum
Moving away from the funding_txid opens the way for splicing + rbf
