Beware of bind9 upgrade on Debian Testing

[Tadas]

If you are using Debian testing with Samba AD DC and DLZ backend beware and
do not upgrade to latest bind9 version. Maintainers disabled dlopen :/

http://packages.debian.org/changelogs/pool/main/b/bind9/current/changelog

   [Matthew Grant]

   * Turn off dlopen as it was causing test compile failures.
   * Add missing library .postrm files for debhelper

Tadas Barzdžius