fix: use Stackable Maven repository in Hadoop build

[dervoeti]

Description

Hadoop was accidentally built as root, with the side effect that our custom Maven repository was not used.
This PR fixes two things:

• Build Hadoop as stackable
• Make root use our custom Maven repository as well, just to be safe

I tested the new Maven settings for root separately by running the Hadoop build as root and analyzing with Wireshark that packets go out to 5.250.180.85 (the current address of build-repo.stackable.tech), which was the case, so the settings seem to work for root.

Definition of Done Checklist

Note

Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant.

Please make sure all these things are done and tick the boxes

• Changes are OpenShift compatible
• All added packages (via microdnf or otherwise) have a comment on why they are added
• Things not downloaded from Red Hat repositories should be mirrored in the Stackable repository and downloaded from there
• All packages should have (if available) signatures/hashes verified
• Add an entry to the CHANGELOG.md file
• Integration tests ran successfully

TIP: Running integration tests with a new product image

The image can be built and uploaded to the kind cluster with the following commands:

bake --product <product> --image-version <stackable-image-version>
kind load docker-image <image-tagged-with-the-major-version> --name=<name-of-your-test-cluster>

See the output of bake to retrieve the image tag for <image-tagged-with-the-major-version>.

[lfrancke]

Related #1132