HDDS-11820. Remove hard-coded principals from ozone-testkrb5

[adoroszlai]

What changes were proposed in this pull request?

Test user principals are currently defined in the apache/ozone-docker-testkrb5 repository. Whenever a new principal is needed for tests, we need to:

• commit updated init.sh in apache/ozone-docker-testkrb5
• bump ozone-testkrb5 image version in apache/ozone
• update keytabs in apache/ozone (this steps is removed in HDDS-11810)

This can be improved by creating principals just-in-time, right before exporting keytabs.

Benefits:

• simplifies the process of adding new principals
• avoid mismatch in list of principals added and exported

This PR removes hard-coded principals from the ozone-testkrb5 image.

https://issues.apache.org/jira/browse/HDDS-11820

How was this patch tested?

Ran secure acceptance tests with this image and corresponding Ozone change:
https://github.com/adoroszlai/ozone/actions/runs/12067118583

[dombizita]

Thanks for this improvement @adoroszlai! It'll be way easier this way. If others check this later, the corresponding Ozone side change is apache/ozone#7498, right?

[adoroszlai]

Thanks @dombizita for the review.

the corresponding Ozone side change is apache/ozone#7498, right?

That one is a pre-requisite for this, but another PR will follow after this image is available. In addition to updating the image, the only Ozone-side change will be: adoroszlai/ozone@bc23d0c