gdm: update default service when smartcard inserted

Early on at start up we may not know if a smartcard is
available.  Make sure we reupdate the default service
after we get a smartcard insertion event.

js/gdm/util.js

@@ -335,6 +335,8 @@ var ShellUserVerifier = new Lang.Class({
             else if (this._preemptingService == SMARTCARD_SERVICE_NAME)
                 this._preemptingService = null;
 
+            this._updateDefaultService();
+
             this.emit('smartcard-status-changed');
         }
     },