message: [consensus] Do not print stack trace when fetch failed
  This stack trace is useless and pollutes log
  Closes:
  Approved by: dmitri-perelman
diff: @@ -238,7 +238,7 @@ impl<T: Payload> EventProcessor<T> {
  .await
  {
  warn!(
  - "Dependencies of proposal {} could not be added to the block store: {:?}",
  + "Dependencies of proposal {} could not be added to the block store: {}",
  proposal_msg, e
  );
  return None;
  @@ -360,7 +360,7 @@ impl<T: Payload> EventProcessor<T> {
  .await
  .map_err(|e| {
  warn!(
  - "Fail to sync up to HQC @ round {}: {:?}",
  + "Fail to sync up to HQC @ round {}: {}",
  sync_info.hqc_round(),
  e
  );
  @@ -383,7 +383,7 @@ impl<T: Payload> EventProcessor<T> {
  counters::SYNC_INFO_MSGS_RECEIVED_COUNT.inc();
  // To avoid a ping-pong cycle between two peers that move forward together.
  if let Err(e) = self.sync_up(&sync_info, peer, false).await {
  - error!("Fail to process sync info: {:?}", e);
  + error!("Fail to process sync info: {}", e);
  }
  }
  @@ -744,14 +744,14 @@ impl<T: Payload> EventProcessor<T> {
  .fetch_quorum_cert(qc.as_ref().clone(), preferred_peer, deadline)
  .await
  {
  - error!("Error syncing to qc {}: {:?}", qc, e);
  + error!("Error syncing to qc {}: {}", qc, e);
  return None;
  }
  } else if let Err(e) = self
  .block_store
  .insert_single_quorum_cert(qc.as_ref().clone())
  {
  - error!("Error inserting qc {}: {:?}", qc, e);
  + error!("Error inserting qc {}: {}", qc, e);
  return None;
  }
  self.process_certificates(qc.as_ref(), None).await;
  