fix(tests): return SCAP_TIMEOUT instead of an SCAP_EOF

[Andreagit97]

What type of PR is this?

/kind bug

Any specific area of the project related to this PR?

/area tests

Does this PR require a change in the driver versions?

No

What this PR does / why we need it:

When the engine test doesn't produce any events but receives events from an async plugin the events in the queue are never processed because the test engine in fetch_next_event will always return SCAP_EOF and so the events will be never dequeued...

	int32_t res = SCAP_SUCCESS;
	if (m_delayed_scap_evt.empty())
	{
		res = m_delayed_scap_evt.next(m_h);
	}

	if (res == SCAP_TIMEOUT &&
		!m_async_events_queue.empty() && m_async_events_queue.try_pop(m_async_evt))
	{
		evt = m_async_evt.get();
		if(evt->m_pevt->ts == (uint64_t) -1)
		{
			evt->m_pevt->ts = get_new_ts();
		}
		return SCAP_SUCCESS;
	}

Moreover SCAP_TIMEOUT seems a more reasonable value to return than SCAP_EOF

Which issue(s) this PR fixes:

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

[FedeDP]

/approve

[poiana]

LGTM label has been added.

Git tree hash: ea8897beee951df9cb99310f028818d64e7fcccb

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Andreagit97, FedeDP, jasondellaluce

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• OWNERS [Andreagit97,FedeDP,jasondellaluce]

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