tests/docker: use project specific container registries

Since Docker Hub has started to enforce pull rate limits on clients, it
is preferrable to use project specific container registries where they
are available. Fedora and OpenSUSE projects provide registries.

The images in these registries are also refreshed on a more regular
basis than the ones in docker hub, so the package update should
generally be faster.

While CentOS also has a registry it is considerably outdated compared
to docker.io, and also only provides x86 images, while docker.io images
are multi-arch.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
Reviewed-by: Willian Rampazzo <willianr@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20210623142245.307776-4-berrange@redhat.com>
Message-Id: <20210709143005.1554-12-alex.bennee@linaro.org>