message: Remove `set_is_shutting_down` method
diff: @@ -719,7 +719,7 @@ where
  match TERMINATION_REQUESTED.load(Ordering::SeqCst) as i32 {
  0 => {
  if let Some(reactor_exit) = self.reactor.maybe_exit() {
  - self.set_is_shutting_down();
  + self.is_shutting_down.set();
  // TODO: Workaround, until we actually use control announcements for
  // exiting: Go over the entire remaining event queue and look for a control
  @@ -753,15 +753,15 @@ where
  }
  }
  SIGINT => {
  - self.set_is_shutting_down();
  + self.is_shutting_down.set();
  break ReactorExit::ProcessShouldExit(ExitCode::SigInt);
  }
  SIGQUIT => {
  - self.set_is_shutting_down();
  + self.is_shutting_down.set();
  break ReactorExit::ProcessShouldExit(ExitCode::SigQuit);
  }
  SIGTERM => {
  - self.set_is_shutting_down();
  + self.is_shutting_down.set();
  break ReactorExit::ProcessShouldExit(ExitCode::SigTerm);
  }
  _ => error!("should be unreachable - bug in signal handler"),
  @@ -770,19 +770,14 @@ where
  }
  /// Shuts down a reactor, sealing and draining the entire queue before returning it.
  - pub(crate) async fn drain_into_inner(mut self) -> R {
  - self.set_is_shutting_down();
  + pub(crate) async fn drain_into_inner(self) -> R {
  + self.is_shutting_down.set();
  self.scheduler.seal();
  for (ancestor, event) in self.scheduler.drain_queues().await {
  debug!(?ancestor, %event, "drained event");
  }
  self.reactor
  }
  -
  - /// Sets the "reactor is shutting down" flag.
  - fn set_is_shutting_down(&mut self) {
  - self.is_shutting_down.set()
  - }
  }
  #[cfg(test)]
  