invoice: Fix waitanyinvoice

There were two bugs: we weren't returning the next from the given
label but the one matching the label, and we were appending new
invoices to the head instead of the tail, which meant we'd be
traversing in the wrong order.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

lightningd/invoice.c

@@ -191,7 +191,7 @@ static void json_invoice(struct command *cmd,
 
 	/* OK, connect it to main state, respond with hash */
 	tal_steal(invs, invoice);
-	list_add(&invs->invlist, &invoice->list);
+	list_add_tail(&invs->invlist, &invoice->list);
 
 	json_object_start(response, NULL);
 	json_add_hex(response, "rhash",
@@ -342,6 +342,8 @@ static void json_waitanyinvoice(struct command *cmd,
 			command_fail(cmd, "Label not found");
 			return;
 		}
+		/* Skip this particular invoice */
+		i = list_next(&invs->invlist, i, list);
 		while (i && i->state == UNPAID) {
 			i = list_next(&invs->invlist, i, list);
 		}