NetworkMenu: hide the "Turn On" item when the rfkill is hardware blocked

If wifi is disabled in hardware, there is nothing we can do at
the sw level, so hide the menu item.

https://bugzilla.gnome.org/show_bug.cgi?id=709635

js/ui/status/network.js

@@ -1058,6 +1058,7 @@ const NMDeviceWireless = new Lang.Class({
 
     _sync: function() {
         this._toggleItem.label.text = this._client.wireless_enabled ? _("Turn Off") : _("Turn On");
+        this._toggleItem.actor.visible = this._client.wireless_hardware_enabled;
 
         this.item.status.text = this._getStatus();
         this.item.icon.icon_name = this._getMenuIcon();