Fix secret deployment for test machines in our NixOS vm and container
tests.
We filter now if we really need to deploy a certain set of files as a
deployment script, which alleviates us running into these edgecases:
```
error: The option `nodes.server.system.activationScripts.setupSecrets.text'
was accessed but has no value defined. Try setting the option.
```
0a56f60005