weather: Take global location switch into account

weather: Take global location switch into account

The setting to globally disable location settings altogether isn't
handled by the geoclue service itself, but by the authorization
agent. This means that:

 - it doesn't apply to system components
   (which gnome-shell is now considered[0])
 - it doesn't apply once the geoclue connection
   has been authorized

However users can reasonably expect that we won't use location services
after they disabled them, so handle the setting explicitly.

[0] https://cgit.freedesktop.org/geoclue/commit/?id=a4cef6c0ad08

https://bugzilla.gnome.org/show_bug.cgi?id=780252