message: clarify no_data_race_after_complete test
diff: @@ -148,6 +148,7 @@ fn no_data_race_after_complete() {
  let reader = thread::spawn(move || unsafe {
  let mut pending = 0;
  + // this doesn't block because reader only executes after `InitOnceComplete` is called
  assert_eq!(InitOnceBeginInitialize(init_once_ptr.0, 0, &mut pending, null_mut()), TRUE);
  assert_eq!(pending, FALSE);
  // this should not data race
  @@ -162,9 +163,8 @@ fn no_data_race_after_complete() {
  unsafe {
  assert_eq!(InitOnceComplete(init_once_ptr.0, 0, null_mut()), TRUE);
  }
  - //println!("complete");
  - // run reader
  + // run reader (without preemption, it has not taken a step yet)
  assert_eq!(reader.join().unwrap(), 1);
  }
  