Netevent driver tests print received events without validating their contents

[lakshk98]

The netevent driver tests currently print each event received from the perf buffer but do not validate most of its contents. The per-event output also generates large, interleaved CI logs and slows perf-buffer processing. Combined with asynchronous callbacks and fixed sleeps, this can leave events queued while the test captures counter snapshots or transitions between flow and drop phases, causing intermittent assertion failures.

[shankarseal]

Apart from the fixes to the problems you mentioned above, I think the tests should also move to the poll-model instead of the automatic callbacks.

This issue is marked with "low" priority and is scheduled for 2611. If you want to expedite it, please remove the triage field so that we can have a discussion in the next triage meeting.