Allow funding errors in full_stack_target fuzzer

When a channel gets replaced before we can fund it, its possible
now (due to RNG output repetition) to hit the "trying to fund
channel before its ready to be funded" error in the
`full_stack_target` fuzzer.

Thus, we now simply ignore errors when funding.

Author: TheBlueMatt

fuzz/src/full_stack.rs

@@ -857,21 +857,15 @@ pub fn do_test(mut data: &[u8], logger: &Arc<dyn Logger>) {
 				}
 				if tx.version.0 <= 0xff && !channels.is_empty() {
 					let chans = channels.iter().map(|(a, b)| (a, b)).collect::<Vec<_>>();
-					if let Err(e) =
-						channelmanager.batch_funding_transaction_generated(&chans, tx.clone())
-					{
-						// It's possible the channel has been closed in the mean time, but any other
-						// failure may be a bug.
-						if let APIError::ChannelUnavailable { .. } = e {
-						} else {
-							panic!();
+					let res =
+						channelmanager.batch_funding_transaction_generated(&chans, tx.clone());
+					if res.is_ok() {
+						let funding_txid = tx.compute_txid();
+						for idx in 0..tx.output.len() {
+							let outpoint = OutPoint { txid: funding_txid, index: idx as u16 };
+							pending_funding_signatures.insert(outpoint, tx.clone());
 						}
 					}
-					let funding_txid = tx.compute_txid();
-					for idx in 0..tx.output.len() {
-						let outpoint = OutPoint { txid: funding_txid, index: idx as u16 };
-						pending_funding_signatures.insert(outpoint, tx.clone());
-					}
 				}
 			},
 			11 => {