Reworked the renaming mechanism
    
    The rename operation on *_mod commands was only allowed when
    the primary key of an entry was also its RDN. With these changes,
    it should be possible to rename the rest of the entries as well.
    
    An attribute to the base LDAPObject was added to whitelist the
    objects we want to allow to be renamed. It replaced an old
    attribute rdn_is_primary_key which was used for the very same
    purpose but the name was confusing because it was not set
    correctly for certain objects.
    
    https://pagure.io/freeipa/issue/2466
    https://pagure.io/freeipa/issue/6784
    
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>
    Reviewed-By: Martin Basti <mbasti@redhat.com>