onchaind: remove htlcs when peer is irrevocably committed.

We don't track them accurately when in onchaind, but we don't want to:
onchaind can be restarted at any time.

Once it's all settled, we're clear to clean them up.

Before this, valgrind could complain about deferncing hout->key.peer:

Valgrind error file: valgrind-errors.10876
==10876== Invalid read of size 4
==10876==    at 0x41F8AF: peer_on_chain (peer_control.h:127)
==10876==    by 0x42340D: notify_new_block (peer_htlcs.c:1461)
==10876==    by 0x40A08D: connect_block (chaintopology.c:96)
==10876==    by 0x40A96B: topology_changed (chaintopology.c:313)
==10876==    by 0x40AC85: add_block (chaintopology.c:384)
==10876==    by 0x40ABF0: gather_previous_blocks (chaintopology.c:363)
==10876==    by 0x4051B3: process_rawblock (bitcoind.c:410)
==10876==    by 0x4044DD: bcli_finished (bitcoind.c:155)
==10876==    by 0x454665: destroy_conn (poll.c:183)
==10876==    by 0x454685: destroy_conn_close_fd (poll.c:189)
==10876==    by 0x45DF89: notify (tal.c:240)
==10876==    by 0x45E43A: del_tree (tal.c:400)
==10876==  Address 0x6929208 is 2,120 bytes inside a block of size 2,416 free'd
==10876==    at 0x4C2EDEB: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==10876==    by 0x45E513: del_tree (tal.c:421)
==10876==    by 0x45E849: tal_free (tal.c:509)
==10876==    by 0x41A8E9: handle_irrevocably_resolved (peer_control.c:1172)

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/peer_control.c

@@ -1165,6 +1165,36 @@ static void handle_onchain_htlc_timeout(struct peer *peer, const u8 *msg)
 
 static void handle_irrevocably_resolved(struct peer *peer, const u8 *msg)
 {
+	struct htlc_out_map_iter outi;
+	struct htlc_out *hout;
+	struct htlc_in_map_iter ini;
+	struct htlc_in *hin;
+	bool deleted;
+
+	/* FIXME: Implement check_htlcs to ensure no dangling hout->in ptrs! */
+
+	do {
+		deleted = false;
+		for (hout = htlc_out_map_first(&peer->ld->htlcs_out, &outi);
+		     hout;
+		     hout = htlc_out_map_next(&peer->ld->htlcs_out, &outi)) {
+			if (hout->key.peer != peer)
+				continue;
+			tal_free(hout);
+			deleted = true;
+		}
+
+		for (hin = htlc_in_map_first(&peer->ld->htlcs_in, &ini);
+		     hin;
+		     hin = htlc_in_map_next(&peer->ld->htlcs_in, &ini)) {
+			if (hin->key.peer != peer)
+				continue;
+			tal_free(hin);
+			deleted = true;
+		}
+		/* Can skip over elements due to iterating while deleting. */
+	} while (deleted);
+
 	/* FIXME: Remove peer from db. */
 	log_info(peer->log, "onchaind complete, forgetting peer");