nsscash: store and check hash of deployed files

nsscash: store and check hash of deployed files

The goal is to detect manual modifications of the deployed files. As we
store only the last modification in the state file and don't check the
deployed file itself, modifications go unnoticed.

An alternative would be to check the last modification time of the
deployed files. But a hash is safer as possible corruptions to the file
are detected as well.