delegate the indentation handling in advises to dedicated class
    
    Indentation levels are now handled transparently by a dedicated class
    and should not pollute the statement printing logic.
    
    https://pagure.io/freeipa/issue/7036
    
    Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>