The current fedora 22 docker image is actual fedora 20. So dnf command does not work.
Linux 5440e8f7467f 3.19.3-100.fc20.x86_64 #1 SMP Fri Mar 27 16:53:47 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
This is what actually in fedora22 docker image.
This is known, it's incorrect. Following up upstream.
For reference, nothing here has changed: https://github.com/docker-library/official-images/blame/master/library/fedora
Issue was found upstream, the docker team has reported it's been fixed and is being pushed.
Thank you for the BZ.