docker: set default parameters values

[drupol]

Should fix #13443

Motivation

Context

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[edolstra]

I'm not sure whether we should be exposing docker.nix at all, since AFAIK it's intended to be internal to our release process. And we definitely shouldn't document non-reproducible build instructions like

nix build --file docker.nix

(i.e. non-flake and depending on <nixpkgs>.)

[drupol]

Hello,

Let me know what I could do to improve the situation and I'll gladly do it.

IMO, I still believe that this is a good thing to expose the OCI container which is the official docker image pushed on hub.docker.com.

[tomberek]

This is fixing an existing problem. Removing this interface or removing from docs can be another PR if desired.