avahi: apply fix for CVE-2021-3468

This patch isn't yet upstream but it has been submitted and other distros
are shipping it.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit ea33a4a2)
Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>