CVE-2020-25717: Add FreeIPA domain controller role

CVE-2020-25717: Add FreeIPA domain controller role

As we want to reduce use of 'classic domain controller' role but FreeIPA
relies on it internally, add a separate role to mark FreeIPA domain
controller role.

It means that role won't result in ROLE_STANDALONE.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14801
BUG: https://bugzilla.samba.org/show_bug.cgi?id=14556

Pair-Programmed-With: Stefan Metzmacher <metze@samba.org>

Signed-off-by: Alexander Bokovoy <ab@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>