Make sure our packages don't conflict with EPEL backports
In Hyperscale, systemd-boot and systemd-timesyncd are provided by
systemd-udev so let's make sure that we don't have conflicts when
installing Hyperscale on a systemd with either of these packages
installed by conflicting/obsoleting/providing these packages from
systemd-udev.
Similarly, let's make sure epel-rpm-macros-systemd doesn't conflict
with rpm-macros-systemd using the same approach.
To make sure we can merge the previous networkd package fixes into
the c9s branch, we make it conditional on the stream version we're
building for.