message: Confirmation should be sent only for lambda message.
diff: @@ -163,6 +163,7 @@ impl<C: Context> ActiveValidator<C> {
  let r_exp = self.round_exp(state, timestamp);
  timestamp >> r_exp == vote.timestamp >> r_exp // Current round.
  && state.leader(vote.timestamp) == vote.creator // The creator is the round's leader.
  + && vote.timestamp == round_id(vote.timestamp, vote.round_exp) // Check if it's a lambda message.
  && vote.creator != self.vidx // We didn't send it ourselves.
  && !state.has_evidence(vote.creator) // The creator is not faulty.
  && self.latest_vote(state)
  