coin-moves: only log htlc_timeout pair for penalty txs

We cleanup our output tracking for timeout txs when the peer's
htlc_timeout self-expiry is hit; we'd also log its spend if happen to
see it get spent.

This is a bit of a race as they can't spend it until the locktime is
available. Hence the flakiness in tests that expected the `htlc_timeout`
to *not* be spent.

Instead, we only log an external's `htlc_timeout` spend in the case
where we also immediately register another output to track for it (only
happens when said htlc is stealable)

Fixes #5405
In-Collab-With: @ddustin

onchaind/onchaind.c

@@ -1727,12 +1727,12 @@ static void output_spent(struct tracked_output ***outs,
 			break;
 
 		case THEIR_HTLC:
-			record_external_deposit(out, out->tx_blockheight,
-						HTLC_TIMEOUT);
-			record_external_spend(&tx_parts->txid, out,
-					      tx_blockheight, HTLC_TIMEOUT);
-
 			if (out->tx_type == THEIR_REVOKED_UNILATERAL) {
+				record_external_deposit(out, out->tx_blockheight,
+							HTLC_TIMEOUT);
+				record_external_spend(&tx_parts->txid, out,
+						      tx_blockheight, HTLC_TIMEOUT);
+
 				/* we've actually got a 'new' output here */
 				steal_htlc_tx(out, outs, tx_parts,
 					      tx_blockheight,

tests/test_closing.py

@@ -2520,7 +2520,6 @@ def test_onchain_feechange(node_factory, bitcoind, executor):
     assert only_one(l2.rpc.listinvoices('onchain_timeout')['invoices'])['status'] == 'unpaid'
 
 
-@pytest.mark.skip("Lisa, please fix this!")
 @pytest.mark.developer("needs DEVELOPER=1 for dev-set-fees")
 def test_onchain_all_dust(node_factory, bitcoind, executor):
     """Onchain handling when we reduce output to all dust"""