De-duplicate ACI attributes and permissions
    
    Ensure uniqueuess in attributes and permissions in the ACI class.
    
    A set() is not used because it doesn't guarantee order which ends up
    causing cascading and unpredictable test failures. Since all we
    really need is de-duplication and not a true mathematical set iterating
    through the list is sufficiently fast, particularly since the number
    of elements will always be low.
    
    https://pagure.io/freeipa/issue/8443
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>