The only places which should call try_reconnect now are the "connect"
command, and the disconnect path when it decides there's still an
active channel.
This introduces one subtlety: if we disconnect when there's no active
channel, but then the subd makes one, we have to catch that case!
This temporarily reverts "slow" reconnections to fast ones: see next
patch.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>