network: Update the icon in the panel whenever NM's state changes

Similar to what it's done when the main connection changes, we need
to make sure that the icon in the panel gets updated before calling
_syncConnectivity(), so that the icon gets always updated if needed,
regardless of whether there's an active connection or not.

This is needed because there's at least one case when an icon should
be shown when the computer is not connected to any network: when a
hotspot has been enabled, which can be useful even if there's not
an internet connection to share (e.g. to easily allow connecting
other devices to the computer.

Closes: https://gitlab.gnome.org/GNOME/gnome-shell/issues/214

js/ui/status/network.js

@@ -1944,6 +1944,7 @@ var NMApplet = new Lang.Class({
         this.indicators.visible = this._client.nm_running;
         this.menu.actor.visible = this._client.networking_enabled;
 
+        this._updateIcon();
         this._syncConnectivity();
     },