Bug 2216790

Description of problem:
The systemd units created by rbldnsctl use the `.include` directive, which was deprecated in 2014, started generating warnings in 2018 (https://github.com/systemd/systemd/commit/41b283d0f1f4abd85d0bbeeb7f71bb30f87cfab9) and was removed completely in systemd v246 (https://github.com/systemd/systemd/commit/7ade8982ca1969e251a29589ae918c3b5c595afb).

Because the .include has no effect on modern version of systemd these units have no installation config and cannot be enabled using systemctl.

Version-Release number of selected component (if applicable):


How reproducible:
Always.

Steps to Reproduce:
1. echo 'RBLDNSD="- -q"' > /etc/sysconfig/rbldnsd
2. rbldnsctl create
3. systemctl enable rbldnsd-single.service

Actual results:
systemctl does not enable the service and outputs:

The unit files have no installation config (WantedBy=, RequiredBy=, Also=,
Alias= settings in the [Install] section, and DefaultInstance= for template
units). This means they are not meant to be enabled or disabled using systemctl.

Possible reasons for having this kind of units are:
• A unit may be statically enabled by being symlinked from another unit's
  .wants/ or .requires/ directory.
• A unit's purpose may be to act as a helper for some other unit which has
  a requirement dependency on it.
• A unit may be started when needed via activation (socket, path, timer,
  D-Bus, udev, scripted systemctl call, ...).
• In case of template units, the unit is meant to be enabled with some
  instance name specified.

Expected results:
Created symlink /etc/systemd/system/multi-user.target.wants/rbldnsd-single.service → /etc/systemd/system/rbldnsd-single.service.

Additional info:
This package should probably use a template unit (https://fedoramagazine.org/systemd-template-unit-files/) to support multiple instances, instead of a custom script that manages individual service units.