fix: Don't print Superset admin credentials during startup

[sbernauer]

Description

Fixes https://github.com/stackabletech/internal-issues/issues/85

First commit is just making script better readable in k8s.
Actual fix is wrapping the command leaking the credentials with set +x and set -x.

Ideally we want a test for this, but I don't know how to test this (other than grepping for the password in the logs)

Definition of Done Checklist

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Author

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1. Changes are OpenShift compatible
2. CRD changes approved
3. CRD documentation for all fields, following the style guide.
4. Helm chart can be installed and deployed operator works
5. Integration tests passed (for non trivial changes)
6. Changes need to be "offline" compatible

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1. Code contains useful comments
2. Code contains useful logging statements
3. (Integration-)Test cases added
4. Documentation added or updated. Follows the style guide.
5. Changelog updated
6. Cargo.toml only contains references to git tags (not specific commits or branches)

Acceptance

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1. Feature Tracker has been updated
2. Proper release label has been added
3. Roadmap has been updated

[maltesander]

LGTM!