[HttpClient] fix management of shorter-than-requested timeouts with AmpHttpClient

Author: nicolas-grekas

Test/Fixtures/web/index.php

@@ -116,7 +116,7 @@
         echo '<1>';
         @ob_flush();
         flush();
-        usleep(600000);
+        usleep(500000);
         echo '<2>';
         exit;
 

Test/HttpClientTestCase.php

@@ -745,7 +745,7 @@ public function testTimeoutIsNotAFatalError()
         usleep(300000); // wait for the previous test to release the server
         $client = $this->getHttpClient(__FUNCTION__);
         $response = $client->request('GET', 'http://localhost:8057/timeout-body', [
-            'timeout' => 0.3,
+            'timeout' => 0.25,
         ]);
 
         try {