Shift more Hiera stuff around

Remove everything specific to staging and production. They'll get their
data from elsewhere.

Get rid of the role_env hiera layer. The only thing still using it was
setting ntp servers for the etcd node in staging. This is now done by
way of upstream_ntp_servers which only applies to the etcd role.
I'm happy to remove this, but it seems like it might come into handy at some point.