[FLINK-38536][tests] Add debugging for test failure

[davidradl]

What is the purpose of the change

Add logging so we can see more information about the cause of the test failure reported in FLINK-38536

Brief change log

• add logging to test

Verifying this change

Please make sure both new and modified tests in this PR follow the conventions for tests defined in our code quality guide.

*amended existing unit test to add logging

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): ( no)
• The serializers: (no)
• The runtime per-record code paths (performance sensitive): (no)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (no)
• The S3 file system connector: ( no)

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)

[flinkbot]

CI report:

• ade0be9 Azure: FAILURE

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot run azure re-run the last Azure build

[davidradl]

@flinkbot run azure

[ruanhang1993]

LGTM. @davidradl We need to rebase the master branch to let the tests pass.

[davidradl]

@ruanhang1993 No conflicts with base indicates it can merge; so no need to rebase. I did git pull upstream master --rebase there is nothing to push. The error on the CI seems to be an unrelated Python error - another CI test instability issue I think.

[ruanhang1993]

This PR just add some logs to debug. Merge.