fix: Include hdfs principal names in discovery ConfigMap

[sbernauer]

Description

Replaces #424
Fixes #419

Definition of Done Checklist

• 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

# Author
- [x] Changes are OpenShift compatible
- [x] CRD changes approved
- [x] CRD documentation for all fields, following the [style guide](https://docs.stackable.tech/home/nightly/contributor/style-guide).
- [x] Helm chart can be installed and deployed operator works
- [ ] Integration tests passed (for non trivial changes)
- [x] Changes need to be "offline" compatible

# Reviewer
- [x] Code contains useful comments
- [x] Documentation added or updated. Follows the [style guide](https://docs.stackable.tech/home/nightly/contributor/style-guide).
- [x] Changelog updated
- [x] Cargo.toml only contains references to git tags (not specific commits or branches)

# Acceptance
- [ ] Feature Tracker has been updated
- [x] Proper release label has been added

[siegfriedweber]

LGTM

[sbernauer]

Thanks for the review!