message: Fix bug in ActiveValidator::round_exp.
diff: @@ -262,7 +262,7 @@ impl<C: Context> ActiveValidator<C> {
  fn round_exp(&self, state: &State<C>, timestamp: Timestamp) -> u8 {
  self.latest_vote(state).map_or(self.next_round_exp, |vote| {
  let max_re = self.next_round_exp.max(vote.round_exp);
  - if timestamp < round_id(timestamp, max_re) {
  + if vote.timestamp < round_id(timestamp, max_re) {
  self.next_round_exp
  } else {
  vote.round_exp
  