objectManager: clear inhibitor on unregistered interfaces

A D-Bus service can export more supported interfaces than the
shell cares about.  In those cases, we avoid creating proxies,
but neglect to finish things up so the object manager class
knows it can mark itself loaded.

This commit makes sure we do the proper finishing, so the object
manager still loads in the face of unsupported interfaces.

https://bugzilla.gnome.org/show_bug.cgi?id=706542

js/misc/objectManager.js

@@ -73,8 +73,11 @@ const ObjectManager = new Lang.Class({
     _addInterface: function(objectPath, interfaceName, onFinished) {
            let info = this._interfaceInfos[interfaceName];
 
-           if (!info)
+           if (!info) {
+               if (onFinished)
+                   onFinished();
                return;
+           }
 
            let proxy = new Gio.DBusProxy({ g_connection: this._connection,
                                            g_name: this._serviceName,