GitLab

The Fedora images in the Docker hub container registry are updated less
frequently and lag the ones from Fedora's offical repo.

In my experience, this often leads to periods where our CI testing is
broken on rawhide due to some short-lived issue that is already fixed in
current images.

So, change our Dockerfiles to pull specifically from the upstream
registry.fedoraproject.org instead.
Signed-off-by: Reza Arbab <arbab@linux.ibm.com>
Reviewed-by: Dan Horák <dan@danny.cz>
Reviewed-by: Abhishek Singh Tomar <abhishek@linux.ibm.com>