Consistently exit the overview when launching external applications

We were doing this in one or two places, but not most of them.

https://bugzilla.gnome.org/show_bug.cgi?id=653095

js/ui/status/network.js

@@ -1632,6 +1632,7 @@ NMApplet.prototype = {
         this.menu.addMenuItem(this._devices.vpn.section);
 
         this.menu.addAction(_("Network Settings"), function() {
+            Main.overview.hide();
             let app = Shell.AppSystem.get_default().get_app('gnome-network-panel.desktop');
             app.activate(-1);
         });