Warn people about Alpine based images and DNS bugs

[mrkurt]

Alpine based images have all kinds of DNS lookup issues. We should warn people to not use alpine when they deploy an Alpine based image. This has burned at least 3 people using Node apps in the last month.

[jsierles]

Here are a few links referencing this problem. The first one points to a specific problem with Alpine's lack of support for DNS over TCP.

https://christoph.luppri.ch/fixing-dns-resolution-for-ruby-on-alpine-linux/
https://github.com/gliderlabs/docker-alpine/blob/master/docs/caveats.md#dns
gliderlabs/docker-alpine#8
https://support.cloudbees.com/hc/en-us/articles/360040999471-UnknownHostException-caused-by-DNS-Resolution-issue-with-Alpine-Images

[michaeldwan]

Closing since this hasn't come up in a while.