s4:samba-tool/testparm: add a warning when acting as an AD-DC and not using UTF-8

Signed-off-by: Garming Sam <garming@catalyst.net.nz>
Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Kamen Mazdrashki <kamenim@samba.org>

Autobuild-User(master): Kamen Mazdrashki <kamenim@samba.org>
Autobuild-Date(master): Mon Feb 10 02:26:28 CET 2014 on sn-devel-104