message: transport/send: Fix send_data_ready for Ready state
  Even though there is no tx buf yet, send_data_ready should report true.
  I think this also was wrong for DataSent, as well. Oops.
diff: @@ -362,6 +362,7 @@ enum SendStreamState {
  }
  impl SendStreamState {
  + #[cfg(test)]
  fn tx_buf(&self) -> Option<&TxBuffer> {
  match self {
  SendStreamState::Send { send_buf } => Some(send_buf),
  @@ -554,10 +555,11 @@ impl Sendable for SendStream {
  }
  fn send_data_ready(&self) -> bool {
  - self.state
  - .tx_buf()
  - .map(|buf| buf.data_ready())
  - .unwrap_or(false)
  + match self.state {
  + SendStreamState::Ready => true,
  + SendStreamState::Send { ref send_buf } => send_buf.data_ready(),
  + _ => false,
  + }
  }
  fn close(&mut self) {
  