Avoid a short_to_chan_info read lock in claim_funds_from_hop

In 453ed11 we started tracking the
counterparty's `node_id` in `HTLCPreviousHopData`, however we were
still trying to look it up using `prev_short_channel_id` in
`claim_funds_from_hop`.

Because we now usually have the counterparty's `node_id` directly
accessible, we should skip the `prev_short_channel_id` lookup.

This will also be more important in the next commit where we need
to look up state for our counterparty to generate
`ChannelMonitorUpdate`s whether we have a live channel or not.

Author: TheBlueMatt

lightning/src/ln/channelmanager.rs

@@ -6928,11 +6928,10 @@ where
 		&self, prev_hop: HTLCPreviousHopData, payment_preimage: PaymentPreimage,
 		payment_info: Option<PaymentClaimDetails>, completion_action: ComplFunc,
 	) {
-		let counterparty_node_id =
-			match self.short_to_chan_info.read().unwrap().get(&prev_hop.short_channel_id) {
-				Some((cp_id, _dup_chan_id)) => Some(cp_id.clone()),
-				None => None
-			};
+		let counterparty_node_id = prev_hop.counterparty_node_id.or_else(|| {
+			let short_to_chan_info = self.short_to_chan_info.read().unwrap();
+			short_to_chan_info.get(&prev_hop.short_channel_id).map(|(cp_id, _)| *cp_id)
+		});
 
 		let htlc_source = HTLCClaimSource {
 			counterparty_node_id,