update systemd service file

[deathtrip]

It's better to let directory creation be handled by packaging, instead of executing it on every daemon start. On Arch Linux for example, that directory is already contained in the package.
When that line is removed PermissionsStartOnly=true can go as well, it's deprecated anyway.

[tianon]

FWIW, this should be doable in Debian packaging too most easily/directly via debian/<package>.dirs: https://manpages.debian.org/buster/debhelper/dh_installdirs.1.en.html

(I had a similar "huh, that's interesting" moment while reviewing this service file recently 😄)

[gustavo-iniguez-goya]

The PR can not be accepted as is, because we'd break non-arch installations.

I think that this task should be done from the daemon, otherwise we'll depend on the service manager used by the distro (systemd, sysv, s6, openrc, etc, etc)

[deathtrip]

I don't think removing these lines would break opensnitch. As right now on non-systemd distros, the rules directory still has to be created some other way.