darkman should prefer location from config file if set

When using darkman with location detection via geoclue you can get unexpected results after enabling a VPN. For example, I'm in Europe and it's night time, but I enable a VPN in the USA where it is day time. After a few minutes darkman seems to notice and switches to light mode.

I decided to set my location in ~/.config/darkman/config.yaml. Upon restarting darkman it reads the location from the config file , sets dark mode, and then consults geoclue—which resolves my location as being in the USA—and sets light mode!

If a user has a location hard coded in the config then darkman should not consult geoclue.