message: task: Make scopeguard const
diff: @@ -622,7 +622,7 @@ impl BlockedTaskQueue {
  if let Some(wt) = wakeup_time {
  let first_task = true;
  let mut cursor = self.list.cursor_front_mut();
  - let mut _guard = scopeguard::guard(first_task, |first_task| {
  + let _guard = scopeguard::guard(first_task, |first_task| {
  // If the task is the new first task in the list, update the one-shot timer
  // to fire when this task shall be woken up.
  #[cfg(not(feature = "tcp"))]
  