Switch from killing lnd process on app close to using StopDaemon RPC …

[valentinewallace]

…command

This prevents loss of user data by ensuring safe shutdown of the daemon.

This functionality doesn't work perfectly and improved functionality is waiting on a few changes to be merged into lnd. Users will need to use ctrl-c to quit the app if the RPC call is not available at the time of app close.

[ghost]

Tested this out locally and I'm unable to get [INF] LTND: Shutdown complete message in the logs. I'm also seeing the [error] Caught Main Process Error: errors - not sure if they are related.

I tried closing the app multiple times by:

1. cmd + x
2. just closing the window by clicking the X button

[cfromknecht]

Since we're spawning the child process locally, we may want to consider using SIGINT and bypass the RPC altogether. I know @ERKarl reported that the results were inconsistent in testing, were you able to get more reliable results?

[cfromknecht]

Stopdaemon is kind of nice that it is agnostic to whether lnd is running locally or not, though in the case that we're connecting remote we may not want to call StopDaemon?