When the funding tx reaches depth, update the channel's data to the
"correct" funding transaction info from inflights (if necessary).
This will be necessary if:
- the transaction has been successfully RBF'd and
- the lesser fee transaction is the one successfully mined, OR
- the channel is in the process of being RBF'd
Prior to this, all reconnect logic lived in channeld. If you
disconnected before we finished building a funding transaction, that was
no big deal. Now, however, we're waiting for the funding to lock in in
dualopend, instead of handing straight to channeld to wait.
So we need a way to restart dualopend.
This will make it possible to do RBF, since we can re-start the opening
process in dualopend while waiting for lock-in.
Note the new channel states are being used, DUALOPEND_INIT and
DUALOPEND_AWAITING_LOCKIN, to differentiate from openingd/channeld opens
