1. Use per-case QNAM objects
2. In a slots (connected to QNetworkReplies) - if an error detected - stop
the event loop (no reason to continue waiting) and then do normal
QVERIFY/QCOMPARE things.
3. In tests, check QTest::currentTestFailed after the event loop returned -
if an error was detected by a slot, no need to continue with QCOMPARE/QVERIFY
in the test itself.
Task-number: QTBUG-77053
Change-Id: I3827a629a2749becd3dc6eee7fd6994d96441e65
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>