We used to tell connectd to remember our connect delay, and hand it
back (increased if necessary).
Instead, simply record when we last tried to connect. If it was less
than 10 minutes ago, double delay (up to 5 minutes max), otherwise
reset delay to 1 second.
This covers all scenarios: whether we reconnect then immediately
disconnect, or never successfully connect, it doesn't matter.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Fixes: #5453
22ff007d64