Restart LND on lit startup if failure

[levmi]

If LND fails on litd startup, the LND process should automatically restart. If LND is running in remote mode, we should attempt to re-connect. We should attempt this restart in perpetuity, but have a timeout with regard to how often restart attempts occur. When failing to start while restarting, the timeout should be multiplied, so that we attempt to restart less and less often. We can make this configurable.