Add rockylinux9 to integration-tests

[dklimpel]

Checklist

• [x] make test-all (UNIX) passes. CI will also test this
• [x] unit and/or integration tests are included (if applicable)
• [x] documentation is changed or added (if applicable)

Description of change

The image is intended as a replacement for CentOS7. CentOS7 does not run in a github action, rockylinux does.