Suppress expected keepalive errors during test shutdown

[Copilot]

Proposed changes

CI logs are cluttered with keepalive errors (BadServerHalted, BadNoCommunication) during test teardown. These are expected when sessions close during server shutdown and create noise that obscures actual test failures.

Modified ClientFixture.Session_KeepAlive to early-return on these two status codes:

private void Session_KeepAlive(ISession session, KeepAliveEventArgs e)
{
    if (ServiceResult.IsBad(e.Status))
    {
        // Ignore expected errors during test shutdown to reduce noise in CI logs
        if (e.Status?.StatusCode == StatusCodes.BadServerHalted ||
            e.Status?.StatusCode == StatusCodes.BadNoCommunication)
        {
            return;
        }

        m_logger.LogError(
            "Session '{SessionName}' keep alive error: {StatusCode}",
            session.SessionName,
            e.Status?.ToLongString());
    }
}

Other keepalive errors (e.g., BadRequestInterrupted) continue to be logged. Added null-conditional operators for defensive handling.

Related Issues

Issue describes CI logs being full of keepalive error messages during test shutdown.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• Enhancement (non-breaking change which adds functionality)
• Test enhancement (non-breaking change to increase test coverage)
• Breaking change (fix or feature that would cause existing functionality to not work as expected, requires version increase of Nuget packages)
• Documentation Update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc.
• I have signed the CLA.
• I ran tests locally with my changes, all passed.
• I fixed all failing tests in the CI pipelines.
• I fixed all introduced issues with CodeQL and LGTM.
• I have added tests that prove my fix is effective or that my feature works and increased code coverage.
• I have added necessary documentation (if appropriate).
• Any dependent changes have been merged and published in downstream modules.

Further comments

Change is test-only and does not affect production code behavior. No additional tests needed - existing tests verify the fix works (logs are clean on shutdown).

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[Tests] CI Logs are full of LogMessages like Keepalive Error BadSeverhalted / BadNoCommunication</issue_title>
<issue_description>CI Logs are full of LogMessages like Keepalive Error BadSeverhalted / BadNoCommunication.

Those should be ignored by the TestLogger on Test shutdown, to better spot real test errors.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [Tests] CI Logs are full of LogMessages like Keepalive Error BadSeverhalted / BadNoCommunication #3457

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