sharing: Stop assigned services only when no network connection

I've found some situations where the handover service isn't started when it should.

This looks like it happens when network access comes from WiFi. I think it should be started anyway to allow remote login work.

Maybe I'm missing some info and it makes sense not to start the handover service in that situation.

This is related with the discussion from: gnome-remote-desktop!249 (comment 2070445)