If aus_driver_amazon_s3 is loaded, the driver registry does not work.

[susannemoog]

See also andersundsehr/aus_driver_amazon_s3#107

if both extensions are loaded (maybe depending on the loading order) only the amazon_s3 one is shown, as it uses a different way to register the driver (directly via the driver registry).

It might be a good idea to do the same here.