Bump PowerDNS: 4.1.8 → 4.2.2
Bump PowerDNS: 4.1.8 → 4.2.2

Although not reflected in this commit, there have been changes to
`pdns.conf`. See
[here](https://github.com/cunnie/sslip.io/commit/b41435833b7743eb559b0e8af74ecd5bbe96ba08)
for more information.

cunnie/deployments,cunnie/deployments