message: Factor qlog::add_event
  This was sitting there in my editor and I couldn't help noticing the
  repetition.
diff: @@ -61,19 +61,12 @@ impl NeqoQlog {
  where
  F: FnOnce() -> Option<qlog::event::Event>,
  {
  - if let Some(inner) = self.inner.borrow_mut().as_mut() {
  + self.add_event_with_stream(|s| {
  if let Some(evt) = f() {
  - let res = inner.streamer.add_event(evt);
  - if let Err(e) = res {
  - crate::do_log!(
  - ::log::Level::Error,
  - "Qlog streaming failed with error {}; closing qlog.",
  - e
  - );
  - *self.inner.borrow_mut() = None;
  - }
  - }
  + s.add_event(evt)?;
  }
  + Ok(())
  + });
  }
  /// If logging enabled, closure is given the Qlog stream to write events and
  