autopilot/manager: only set m.pilot if started successfully
autopilot/manager: only set m.pilot if started successfully

This commit fixes a subtle bug within the autopilot manager, that would
cause the active pilot to not be reset in case it wasn't started
successfully.

We also make sure the associated goroutines close over the started
pilot, and not the active pilot.

aakselrod/lnd,LightningNetwork/lnd,LightningNetwork/lnd,aakselrod/lnd