The current fedora 22 docker image is actual fedora 20. So dnf command does not work.
uname -a
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.