subd: fix parent of subd.

5c949e3 ("subd: make channel/peer own the subd.")
added a ctx arg, but in fact we steal the subd onto the conn, which is still
allocated off ld!

Hence the memleak that was supposed to fix turned up again in CI!

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

lightningd/subd.c

@@ -711,7 +711,7 @@ static struct subd *new_subd(const tal_t *ctx,
 						 const char *happenings),
 			     va_list *ap)
 {
-	struct subd *sd = tal(ctx, struct subd);
+	struct subd *sd = tal(NULL, struct subd);
 	int msg_fd;
 	const char *debug_subd = NULL;
 	const char *shortname;
@@ -770,7 +770,7 @@ static struct subd *new_subd(const tal_t *ctx,
 	sd->node_id = tal_dup_or_null(sd, struct node_id, node_id);
 
 	/* conn actually owns daemon: we die when it does. */
-	sd->conn = io_new_conn(ld, msg_fd, msg_setup, sd);
+	sd->conn = io_new_conn(ctx, msg_fd, msg_setup, sd);
 	tal_steal(sd->conn, sd);
 
 	log_peer_debug(sd->log, node_id, "pid %u, msgfd %i", sd->pid, msg_fd);