Workaround for proxyChange failing when run alone

The issue itself is not really worth fixing (the very first request
being supposed to have a different proxy than any of the other
following requests before a session has been initiated), but we can
at least make the test pass when it is run alone.

Task-number: QTBUG-63134
Change-Id: I6c7df5c5653541031811e6bff562572061afae0f
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

tests/auto/network/access/qnetworkreply/tst_qnetworkreply.cpp

@@ -5773,6 +5773,15 @@ void tst_QNetworkReply::proxyChange()
     QNetworkRequest req(QUrl("http://" + QtNetworkSettings::serverName()));
     proxyServer.doClose = false;
 
+    {
+        // Needed to initialize a network session in QNAM. Without an initialized session the GET
+        // will be deferred until later, and the proxy will be unset first. This caused the test to
+        // fail in standalone runs (it passed in CI because the same QNAM instance is used for the
+        // entire test).
+        QNetworkReplyPtr temporary(manager.get(req));
+        waitForFinish(temporary);
+    }
+
     manager.setProxy(dummyProxy);
     QNetworkReplyPtr reply1(manager.get(req));
     connect(reply1, SIGNAL(finished()), &helper, SLOT(finishedSlot()));