dns: address compile-time warnings

Signed-off-by: Antoine du Hamel <duhamelantoine1995@gmail.com>
PR-URL: #64355
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Author: aduh95