fix(network-manager): run as a service if systemd module is present

fix(network-manager): run as a service if systemd module is present

In the current state, services that depend on network need to
use dracut hooks, since nothing with pull in the network
targets into the transaction.

In the future, it would be nice to provide developers on systemd-only
systems the possibility to not use dracut hooks at all, but simply put
normal systemd services into the initrd.

Also, some modules even right now depend on systemd ordering, like
cryptsetup, so let's make sure, that the ordering inside systemd work
properly as well.