1) dualopen has fd to connectd
2) channeld needs to take over
3) dualopen passes fd that leads to a connectd over for channeld to use
4) lightningd must receive the fd transfer request and process
5) dualopen shuts down and closes everything it owns
4 & 5 end up in a race. If 5 happens before 4, channeld ends up with an invalid fd for connectd — leaving it in a position to not receive messages.
Lingering for a second makes 4 win the race. Since the daemon is closing anyway, waiting for a second should be alright.
Changelog-Fixed: Fixed a condition for newly created channels that could trigger a need for reconnect.