HDDS-10130. TestSecureOzoneManager.testSecureOmInitFailure fails with Java 17

[adoroszlai]

What changes were proposed in this pull request?

Fix TestSecureOzoneManager failure when run with Java 17 (see HADOOP-17910 for similar issue):

AssertionFailedError: expected: <Can't get SCM signed certificate. omRpcAdd: om-unknown:9862> but was: <Can't get SCM signed certificate. omRpcAdd: om-unknown/<unresolved>:9862>

Additionally, some cleanup (as separate commits).

https://issues.apache.org/jira/browse/HDDS-10130

How was this patch tested?

$ JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64 \
  ./hadoop-ozone/dev-support/checks/junit.sh -DexcludedGroups=unhealthy \
  -am -pl :ozone-integration-test -Dtest='TestSecureOzoneManager'
...
[INFO] Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.891 s -- in org.apache.hadoop.ozone.om.TestSecureOzoneManager

CI (still with Java 8):
https://github.com/adoroszlai/ozone/actions/runs/7538490881

[sodonnel]

LGTM - seems the unresolved error message has changed in JDK 17, so the error we look for is slightly different.

[adoroszlai]

Thanks @sodonnel for the review.