- Only install the init.d service when there is no systemd present:
the systemd service would mask it and only confuses users that
try to debug things.
- Link rc%{name} to /usr/sbin/service when using systemd.
- Move the insserv BuildRequires to be a PreReq (it's not used for
the build system, but actually for the installation on a machine)
and guard it to be validonly for non-systemd systems.

If it were my package I'd probably go even a step further and rip init.d support out