message: fix(server): fix experimental pipeline flushing
diff: @@ -147,7 +147,7 @@ impl<T: Write> Write for Buffered<T> {
  }
  fn flush(&mut self) -> io::Result<()> {
  - if self.flush_pipeline && self.read_buf.is_empty() {
  + if self.flush_pipeline && !self.read_buf.is_empty() {
  Ok(())
  } else if self.write_buf.remaining() == 0 {
  self.io.flush()
  