This eliminates the need the a database to store the hostname policy,
simplifying deployment. We keep the database for now, as part of our
deployability guidelines: we'll deploy, then switch config to the new style.
This also disables the obsolete whitelist checking code, but doesn't yet change
the function signature for policy.New(), to avoid bloating the pull request.
I'll fully remove the whitelist checking code in a future change when I also
remove the policy database code.
Jacob Hoffman-Andrews