rpm-ostreed broken: /var/lib/rpm should be a symlink

With latest rpm-ostree shipped in newer builds the daemon complains about /var/lib/rpm being a dir, not a symlink. Apparently creating this folder in image is against the rpm-ostree filesystem specification.

Also the project lead mentions, that /var should be empty in a deployment. I'm not sure if this also applies to the initial folders we create in an image. While I don't think so, at least /var/lib/rpm shouldn't be there. I'll remove that and release a patch 0.5.2

We should probably do a nightly rebuild of rpm-ostree-engine to account for such upstream problems interfering with this tooling. At least weekly.