Remove largely useless checks in chanmon_consistency fuzzer

When reloading nodes A or C, the chanmon_consistency fuzzer
currently calls `get_and_clear_pending_msg_events` on the node,
potentially causing additional `ChannelMonitor` or `ChannelManager`
updates, just to check that no unexpected messages are generated.

There's not much reason to do so, the fuzzer could always swap for
a different command to call the same method, and the additional
checking requires some weird monitor persistence introspection.

Here we simplify the fuzzer by simply removing this logic.

Author: TheBlueMatt

fuzz/src/chanmon_consistency.rs

@@ -125,7 +125,6 @@ struct TestChainMonitor {
 	// "fails" if we ever force-close a channel, we avoid doing so, always saving the latest
 	// fully-serialized monitor state here, as well as the corresponding update_id.
 	pub latest_monitors: Mutex<HashMap<OutPoint, (u64, Vec<u8>)>>,
-	pub should_update_manager: atomic::AtomicBool,
 }
 impl TestChainMonitor {
 	pub fn new(broadcaster: Arc<TestBroadcaster>, logger: Arc<dyn Logger>, feeest: Arc<FuzzEstimator>, persister: Arc<TestPersister>, keys: Arc<KeyProvider>) -> Self {
@@ -135,7 +134,6 @@ impl TestChainMonitor {
 			keys,
 			persister,
 			latest_monitors: Mutex::new(HashMap::new()),
-			should_update_manager: atomic::AtomicBool::new(false),
 		}
 	}
 }
@@ -146,7 +144,6 @@ impl chain::Watch<TestChannelSigner> for TestChainMonitor {
 		if let Some(_) = self.latest_monitors.lock().unwrap().insert(funding_txo, (monitor.get_latest_update_id(), ser.0)) {
 			panic!("Already had monitor pre-watch_channel");
 		}
-		self.should_update_manager.store(true, atomic::Ordering::Relaxed);
 		self.chain_monitor.watch_channel(funding_txo, monitor)
 	}
 
@@ -162,7 +159,6 @@ impl chain::Watch<TestChannelSigner> for TestChainMonitor {
 		let mut ser = VecWriter(Vec::new());
 		deserialized_monitor.write(&mut ser).unwrap();
 		map_entry.insert((update.update_id, ser.0));
-		self.should_update_manager.store(true, atomic::Ordering::Relaxed);
 		self.chain_monitor.update_channel(funding_txo, update)
 	}
 
@@ -1101,11 +1097,9 @@ pub fn do_test<Out: Output>(data: &[u8], underlying_out: Out) {
 				if !chan_a_disconnected {
 					nodes[1].peer_disconnected(&nodes[0].get_our_node_id());
 					chan_a_disconnected = true;
-					drain_msg_events_on_disconnect!(0);
-				}
-				if monitor_a.should_update_manager.load(atomic::Ordering::Relaxed) {
-					node_a_ser.0.clear();
-					nodes[0].write(&mut node_a_ser).unwrap();
+					push_excess_b_events!(nodes[1].get_and_clear_pending_msg_events().drain(..), Some(0));
+					ab_events.clear();
+					ba_events.clear();
 				}
 				let (new_node_a, new_monitor_a) = reload_node!(node_a_ser, 0, monitor_a, keys_manager_a, fee_est_a);
 				nodes[0] = new_node_a;
@@ -1134,11 +1128,9 @@ pub fn do_test<Out: Output>(data: &[u8], underlying_out: Out) {
 				if !chan_b_disconnected {
 					nodes[1].peer_disconnected(&nodes[2].get_our_node_id());
 					chan_b_disconnected = true;
-					drain_msg_events_on_disconnect!(2);
-				}
-				if monitor_c.should_update_manager.load(atomic::Ordering::Relaxed) {
-					node_c_ser.0.clear();
-					nodes[2].write(&mut node_c_ser).unwrap();
+					push_excess_b_events!(nodes[1].get_and_clear_pending_msg_events().drain(..), Some(2));
+					bc_events.clear();
+					cb_events.clear();
 				}
 				let (new_node_c, new_monitor_c) = reload_node!(node_c_ser, 2, monitor_c, keys_manager_c, fee_est_c);
 				nodes[2] = new_node_c;
@@ -1306,13 +1298,10 @@ pub fn do_test<Out: Output>(data: &[u8], underlying_out: Out) {
 
 		node_a_ser.0.clear();
 		nodes[0].write(&mut node_a_ser).unwrap();
-		monitor_a.should_update_manager.store(false, atomic::Ordering::Relaxed);
 		node_b_ser.0.clear();
 		nodes[1].write(&mut node_b_ser).unwrap();
-		monitor_b.should_update_manager.store(false, atomic::Ordering::Relaxed);
 		node_c_ser.0.clear();
 		nodes[2].write(&mut node_c_ser).unwrap();
-		monitor_c.should_update_manager.store(false, atomic::Ordering::Relaxed);
 	}
 }