Use `/usr/lib/systemd/system` for service file

Seems to be where the party’s at.
Use different env. path for systemd on Debian

`/etc/sysconfig/` seems to be some Fedora specific thingy, though I
think CentOS/RedHat uses the same.
Add `multi-user.target` to systemd service file
Circumvent systemd’s rate limiting, sort of

Apparently there’s a specific amount of times that one is allowed to
start a service within a given time period. Couldn’t manage to disable
it, so instead we wait.
Merge branch 'systemd-fixes'