message: Cancel 'join room' action if 'log in' is clicked
  or 'choose different server'
  We canceled the deferred action in the MatrixChat SetMxId dialog
  but not the one in roomview.
  Fixes
diff: @@ -791,6 +791,9 @@ module.exports = React.createClass({
  if (submitted) {
  this.props.onRegistered(credentials);
  } else {
  + dis.dispatch({
  + action: 'cancel_after_sync_prepared',
  + });
  dis.dispatch({
  action: 'cancel_join',
  });
  