[Consensus] minor fixes (#19742)

## Description 

- Avoid busy looping in commit sync, when failing to fetch from every
peer.
- Make the error to serve connections debug, because the issue is on the
requestor's side.


## Test plan 

CI

---

## Release notes

Check each box that your changes affect. If none of the boxes relate to
your changes, release notes aren't required.

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that describes the impact of your changes that a user might notice and
any actions they must take to implement updates.

- [ ] Protocol: 
- [ ] Nodes (Validators and Full nodes): 
- [ ] Indexer: 
- [ ] JSON-RPC: 
- [ ] GraphQL: 
- [ ] CLI: 
- [ ] Rust SDK:
- [ ] REST API:

consensus/core/src/commit_syncer.rs

@@ -439,13 +439,12 @@ impl<C: NetworkClient> CommitSyncer<C> {
                             .hostname
                             .clone();
                         warn!("Failed to fetch {commit_range:?} from {hostname}: {}", e);
-                        let error: &'static str = e.into();
                         inner
                             .context
                             .metrics
                             .node_metrics
                             .commit_sync_fetch_once_errors
-                            .with_label_values(&[&hostname, error])
+                            .with_label_values(&[&hostname, e.name()])
                             .inc();
                     }
                     Err(_) => {
@@ -466,6 +465,8 @@ impl<C: NetworkClient> CommitSyncer<C> {
                     }
                 }
             }
+            // Avoid busy looping, by waiting for a while before retrying.
+            sleep(TIMEOUT).await;
         }
     }
 

consensus/core/src/network/tonic_network.rs

@@ -829,7 +829,7 @@ impl<S: NetworkService> NetworkManager<S> for TonicManager {
                         match result {
                             Ok(Ok(())) => {},
                             Ok(Err(e)) => {
-                                warn!("Error serving connection: {e:?}");
+                                debug!("Error serving connection: {e:?}");
                             },
                             Err(e) => {
                                 debug!("Connection task error, likely shutting down: {e:?}");