1. In `test_upgrade_downgrade_brokers`, allow duplicates to happen. 2. In `test_version_probing_upgrade`, grep the generation numbers from brokers at the end, and check if they can ever be synchronized.
### Committer Checklist (excluded from commit message) - [ ] Verify design and implementation - [ ] Verify test coverage and CI build status - [ ] Verify documentation (including upgrade notes) [ Full content available at: https://github.com/apache/kafka/pull/5754 ] This message was relayed via gitbox.apache.org for devnull@infra.apache.org
