Zentyal user migration

[davidep (Davide Principi)]

Please refer to this howto

https://wiki.nethserver.org/doku.php?id=howto:add_ns7_samba_domain_controller_to_existing_active_directory&s[]=dc

And this discussion: Add/Replace existing AD Domain Controller with ns7

To demote the old DC: https://wiki.samba.org/index.php/Transferring_and_Seizing_FSMO_Roles