Additional fix for ticket 47526 v3
    
                In modrdn we need to distinguish if the entry is changed is a group or a
                regular memebr of a group. for the group case do the same as when deleting a group
                For the modrdn of an user entry, the case where no memberof attribute exists has
                to succeed.
    
                Reviewed by: noriko, thanks
    
                https://fedorahosted.org/389/ticket/47526