gtkplacesview: don't fetch networks if local only
gtkplacesview: don't fetch networks if local only

We were fetching networks even on local only mode.
Avoid to do extra work if not necessary.

https://bugzilla.gnome.org/show_bug.cgi?id=754150

davidgumberg/gtk,jigpu/gtk,alexlarsson/gtk,jigpu/gtk,jigpu/gtk,grubersjoe/adwaita,jigpu/gtk,chergert/gtk,jadahl/gtk,davidgumberg/gtk,chergert/gtk,jadahl/gtk,alexlarsson/gtk,alexlarsson/gtk,jadahl/gtk,jigpu/gtk,davidgumberg/gtk,alexlarsson/gtk,davidgumberg/gtk,jadahl/gtk,grubersjoe/adwaita,grubersjoe/adwaita,alexlarsson/gtk,chergert/gtk,davidgumberg/gtk,grubersjoe/adwaita,davidgumberg/gtk,chergert/gtk,jigpu/gtk,chergert/gtk,alexlarsson/gtk,jadahl/gtk,davidgumberg/gtk,chergert/gtk,chergert/gtk,alexlarsson/gtk,jadahl/gtk,jigpu/gtk,davidgumberg/gtk,jadahl/gtk,chergert/gtk,grubersjoe/adwaita,grubersjoe/adwaita,jigpu/gtk,grubersjoe/adwaita,alexlarsson/gtk,jadahl/gtk,grubersjoe/adwaita