tst_QHttp2Connection: make settings exchange wait for acknowledgement

Is needed when sending more SETTINGS frames during the test later

Task-number: QTBUG-132277
Pick-to: 6.9 6.8
Change-Id: I24b2a5d1b2e7aecd8687db5b24f37233df3b91dd
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

tests/auto/network/access/qhttp2connection/tst_qhttp2connection.cpp

@@ -153,7 +153,8 @@ bool tst_QHttp2Connection::waitForSettingsExchange(QHttp2Connection *client,
     client->handleReadyRead(); // handle incoming frames, send response
 
     bool success = QTest::qWaitFor([&]() {
-        return settingsFrameReceived && serverSettingsFrameReceived;
+        return settingsFrameReceived && serverSettingsFrameReceived
+                && !client->waitingForSettingsACK && !server->waitingForSettingsACK;
     });
 
     disconnect(c);