Old version missing important bugfix re resolv.conf parsing

[Robert Scott]

The currently packaged version of this is missing this fix: https://github.com/miekg/dns/commit/906238edc6eb0ddface4a1923f6d41ef2a5ca59b which was merged in 2018. Without this fix, tools using this package will panic when attempting to read `resolv.conf` if an `options` line has an 8-character-long value. And unfortunately a recent change to `systemd` (https://github.com/systemd/systemd/commit/a742f9828ea73d9c2c9bafe701c10fe60f058012) which has made it into focal has made this comparatively likely.

In our case this caused the stock ubuntu prometheus from focal (2.15.2+ds-2) to panic on startup one morning.

We've worked around this for now by replacing our `resolv.conf` with a custom one that includes `127.0.0.53` as a nameserver, as per https://jlk.fjfi.cvut.cz/arch/manpages/man/systemd-resolved.8#/ETC/RESOLV.CONF

See our issue enabling this workaround for even more detail: https://github.com/alphagov/prometheus-aws-configuration-beta/pull/440

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.