code: func (c *SessionContext) tryRemoteTLSClient(cluster reversetunnel.RemoteSite) (auth.ClientI, error) {
  	clt, err := c.newRemoteTLSClient(cluster)
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  	_, err = clt.GetDomainName()
  	if err != nil {
  		return clt, trace.Wrap(err)
  	}
  	return clt, nil
  }
docs: // tryRemoteTLSClient tries creating TLS client and using it (the client may not be available
  // due to older clusters), returns client if it is working properly