When multiple units are passed to systemctl and one fails it doesn't
finish the others. Change the template command to call systemctl for
each unit individually.
This also removes the lvm2-activation-generator in runtime-cleanup.tmpl
There's something racy here; in my Atomic Workstation CI/CD I'm seeing:
```
01:12:43 symlink /lib/systemd/system/rngd.service etc/systemd/system/basic.target.wants/rngd.service
01:12:43 FileNotFoundError: [Errno 2] No such file or directory: '/lib/systemd/system/rngd.service' -> '/var/tmp/lorax.7cgdtz1_/installtree/etc/systemd/system/basic.target.wants/rngd.service'
```
Rather than debug this right now, let's just make sure it exists,
like we do right above for `tmp.mount`.
