dns: Fix CID 1034969 Uninitialized scalar variable

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-By: Amitay Isaacs <amitay@gmail.com>

Autobuild-User(master): Amitay Isaacs <amitay@samba.org>
Autobuild-Date(master): Fri Jun 21 17:32:16 CEST 2013 on sn-devel-104