thunderbolt: remove gdbus error prefix, if present

If we get an error during device enrollment, the message might be
prefixed to indicate that the error came from the remote peer. We
are presenting that message to the user so strip that prefix away
if it was there.

js/ui/status/thunderbolt.js

@@ -144,6 +144,7 @@ var Client = new Lang.Class({
 	this._proxy.EnrollDeviceRemote(id, policy, AuthFlags.NONE,
                                        (res, error) => {
 	    if (error) {
+		Gio.DBusError.strip_remote_error(error);
 		callback(null, error);
 		return;
 	    }