requestEnd() is not called in event listener in sync mode.

I converted my timings collector (based on LogHttpArchive) to the new events system and requestEnd() doesn't get called when the last request has finished.

$client = (new Amp\Http\Client\HttpClientBuilder)
    ->usingPool(Amp\Http\Client\Connection\ConnectionLimitingPool::byAuthority(4))
    ->listen(new HttpRequestTimings)
    ->build();

$semaphore = new Amp\Sync\LocalSemaphore(4);

$futures = [];

foreach ($urls as $url) {
	$futures[] = async(function () use ($client, $semaphore, $url) {
		$request = new Request($url);
		$lock = $semaphore->acquire();
		$response = $client->request($request)->getBody()->buffer();
		$lock->release();
	});
}

await($futures);

At this stage requestEnd() has not been called.

However if I add \Amp\delay(0) after await($futures), then requestEnd() is called.

Is this as intended? Should I somehow await for the HTTP client to finish?

Reproduce the provided PHP example using HttpClientBuilder, HttpRequestTimings, await($futures), and the added Amp\delay(0). Trace when requestEnd() is dispatched after the final request in sync mode; done means the listener receives requestEnd() without requiring the extra delay, with behavior covered by a regression test.