verity: prune old broken package from ChromeOS

When we add verity support we will be relying on generic packages such
as cryptsetup instead of whatever unknown bits are in this code base. It
has stopped building and I thought I removed it ages ago. Oops.
Merge pull request #895 from marineam/verity

verity: prune old broken package from ChromeOS
Merge branch 'master' of https://github.com/coreos/coreos-overlay into open-vm-tools