Lint our dockerfiles

[hwine]

Consensus was to add hadolint, but we probably have tuning to do. Our current Dockerfile produces these errors:

Dockerfile:13 DL3005 Do not use apt-get upgrade or dist-upgrade
Dockerfile:13 DL3008 Pin versions in apt get install. Instead of `apt-get install <package>` use `apt-get install <package>=<version>`
Dockerfile:13 DL3009 Delete the apt-get lists after installing something

Do we want to follow the guidance, or ignore these?

• DL3005 - best practice, per Docker
• DL3008 - another best practice from Docker
• DL3009 - ibid

[hwine]

@ajvb @g-k See above for current Dockerfile linting output in frost. Some of those are our common practices.

[hwine]

related- see also this in progress RFC -- improvements welcome