SDAP: Filter ad groups in initgroups
    
    Function sdap_add_incomplete_groups stored domain local groups
    from subdomain as POSIX group, which should not be done.
    
    Resolves:
    https://fedorahosted.org/sssd/ticket/2614
    
    Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
    (cherry picked from commit b9fbeb75e7a4f50f98d979a70a710f9221892483)