s4-torture: Always compile backupkey ndr testsuite.

This removes another incorrect AD_DC_BUILD_IS_ENABLED check ifdef check. The ndr
test is not at all heimdal specific.

Guenther

Signed-off-by: Günther Deschner <gd@samba.org>
Reviewed-by: Alexander Bokovoy <ab@samba.org>
Autobuild-User(master): Alexander Bokovoy <ab@samba.org>
Autobuild-Date(master): Wed May 29 11:29:51 CEST 2013 on sn-devel-104