INI: Unit test for augmentation with empty dir
    
    Merging a configuration with snippets from empty directory should result
    in the same configuration.
    
    Resolves:
    https://pagure.io/SSSD/ding-libs/issue/2776
    
    Meges: https://pagure.io/SSSD/ding-libs/pull-request/3174
    
    Reviewed-by: Alexander Scheel <ascheel@redhat.com>