user.py: replace user_mod with ldap.update_entry()
Refactoring user_add class to use 'ldap.update_entry()' call
instead of api call 'user_mod' when --noprivate option is used.
https://pagure.io/freeipa/issue/5788
Reviewed-By: Martin Basti <mbasti@redhat.com>
Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>