Remove /util/docker folder from v3.3/dev branch (now in dedicated repo)

[bittner]

Removes the entire util/docker folder, which has been migrated to a dedicated repository.

See https://github.com/CRS-support/modsecurity-crs-docker

This PR should be merged after the CRS test suite has been refactored to use the owasp/modsecurity-crs image from Docker Hub, and passes obviously.

Relates to:

• Make ModSecurity CRS repositories easier to manage #1600
• Create automated image builds coreruleset/modsecurity-crs-docker#1
• Travis failure workaround #1684

[bittner]

PR #1684 has just been merged. We should now be safe to remove the util/Docker folder with the legacy Dockerfiles. Any objections?

[dune73]

Not sure the removal is really, really permanent. Let's hold this back a bit more until we are really sure.

(Yes, I know this is all dragging along. Sorry about that.)

[fzipi]

Yes please. I'm porting this to GHA, so wait a little bit longer.

[bittner]

Not sure if we all have the same understanding:

The code from /util/docker is already integrated into the CRS-support/modsecurity-crs-docker and CRS-support/modsecurity-docker projects, which build their respective Docker images automatically.

Removing files here would just be a cleanup measure, and to reduce potential confusion.

We'll integrate more and advance more with those two repositories in the weeks to come.

[fzipi]

I saw and understood that.

For me the problem right now is that we need to be in sync because we used to have a docker that tested properly, but was constructed using a local Dockerfile.

Now moving it away, we need to be sure that our objectives keep being the same (I know it is the CRS support 😄 ), but just to be aware of that.

If we want to remove it, I'm not oppossing to.