HDDS-15177. acceptance test race condition in generating keytab and service start.

[ss77892]

What changes were proposed in this pull request?

HDDS-15177. acceptance test race condition in generating keytab and service start.

Fix intermittent xcompat failures where the new-cluster Compose stack could start SCM and other Kerberos-backed services before init-kdc finished exporting keytabs and starting the KDC. Add the same KDC healthcheck used on the old cluster (verify scm.keytab exists and port 88 accepts connections) and depend on the KDC being healthy.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-15177

How was this patch tested?

CI + local tests.

[adoroszlai]

Thanks @ss77892 for the patch.

[adoroszlai]

Example for failure: https://github.com/apache/ozone/actions/runs/25426543750/job/74600076227

I think other secure clusters need the same fix (only upgrade has it currently). xcompat-old is special only because it starts multiple clusters (one per Ozone version), increasing the probability of hitting the race condition.

[ss77892]

@adoroszlai Thank you for your review and suggestions. I've updated the PR.

[adoroszlai]

Thanks @ss77892 for updating the patch.

[adoroszlai]

I think other secure clusters need the same fix (only upgrade has it currently). xcompat-old is special only because it starts multiple clusters (one per Ozone version), increasing the probability of hitting the race condition.

Adding to remaining tests in #10256.