SNOW-943025: improve flaky OOB test

[sfc-gh-aling]

Please answer these questions before submitting your pull requests. Thanks!

1. What GitHub issue is this PR addressing? Make sure that there is an accompanying issue to your PR.

SNOW-943025, Fixes flaky OOB test

since pytests can run test in parallel and TelemetryService is a singleton, other tests might encounter error logged into the queue of the OOB Telemetry simultaneously leading to assert telemetry.size() == 0 failure, here we check that the OCSP exception event in the test is flushed

2. Fill out the following pre-review checklist:

   • I am adding a new automated test(s) to verify correctness of my new code
   • I am adding new logging messages
   • I am adding a new telemetry message
   • I am modifying authorization mechanisms
   • I am adding new credentials
   • I am modifying OCSP code
   • I am adding a new dependency

3. Please describe how your code solves the related issue.

   Please write a short description of how your code change solves the related issue.

[sfc-gh-stan]

🤔 Do you think we should rewrite the tests or configure some tests to not run in parallel?

[sfc-gh-aling]

@sfc-gh-stan I prefer rewriting the tests (my PR is kinda rewriting the test).
but I don't want to spend time refactoring the whole test suites, so far it's only this test case causing issue.
so I will hold off my efforts until I think it's necessary to do so