Correct channel closed detection in payment state replay

While the case of not having a per-peer-state for a peer that we
have a `ChannelMonitor` with should be unreachable by this point in
`ChannelManager` loading (we have to at least store the latest
update id of the monitor in the peer state), considering a channel
as still-live and not replaying its payment state when we don't
have a per-peer-state is wrong, so here we fix it.

Author: TheBlueMatt

lightning/src/ln/channelmanager.rs

@@ -16455,7 +16455,7 @@ where
 			// First we rebuild all pending payments, then separately re-claim and re-fail pending
 			// payments. This avoids edge-cases around MPP payments resulting in redundant actions.
 			for (channel_id, monitor) in args.channel_monitors.iter() {
-				let mut is_channel_closed = false;
+				let mut is_channel_closed = true;
 				let counterparty_node_id = monitor.get_counterparty_node_id();
 				if let Some(peer_state_mtx) = per_peer_state.get(&counterparty_node_id) {
 					let mut peer_state_lock = peer_state_mtx.lock().unwrap();
@@ -16495,7 +16495,7 @@ where
 				}
 			}
 			for (channel_id, monitor) in args.channel_monitors.iter() {
-				let mut is_channel_closed = false;
+				let mut is_channel_closed = true;
 				let counterparty_node_id = monitor.get_counterparty_node_id();
 				if let Some(peer_state_mtx) = per_peer_state.get(&counterparty_node_id) {
 					let mut peer_state_lock = peer_state_mtx.lock().unwrap();