message: fix(http2): don't consider an h2 send request error as canceled
diff: @@ -117,7 +117,7 @@ where
  Ok(ok) => ok,
  Err(err) => {
  debug!("client send request error: {}", err);
  - let _ = cb.send(Err((::Error::new_canceled(Some(err)), None)));
  + let _ = cb.send(Err((::Error::new_h2(err), None)));
  continue;
  }
  };
  