nspawn: make sure we don't leak the fd in chase_symlinks_and_update

No callers use CHASE_OPEN right now, but let's be defensive.

src/nspawn/nspawn.c

@@ -2233,10 +2233,8 @@ static int chase_symlinks_and_update(char **p, unsigned flags) {
         if (r < 0)
                 return log_error_errno(r, "Failed to resolve path %s: %m", *p);
 
-        free(*p);
-        *p = chased;
-
-        return 0;
+        free_and_replace(*p, chased);
+        return r; /* r might be an fd here in case we ever use CHASE_OPEN in flags */
 }
 
 static int determine_uid_shift(const char *directory) {