Use local result metric instead of global result metric.

This is required for a follow-up commit which adds support for reporting
multiple results in a single benchmark interation.

Change-Id: I8dd7f37ce046cc0f9556be5d0df76f84b82ec1a7
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

src/testlib/qxunittestlogger.cpp

@@ -256,7 +256,7 @@ void QXunitTestLogger::addBenchmarkResult(const QBenchmarkResult &result)
 
     benchmarkElement->addAttribute(
         QTest::AI_Metric,
-        QTest::benchmarkMetricName(QBenchmarkTestMethodData::current->result.metric));
+        QTest::benchmarkMetricName(result.metric));
     benchmarkElement->addAttribute(QTest::AI_Tag, result.context.tag.toUtf8().data());
 
     const qreal valuePerIteration = qreal(result.value) / qreal(result.iterations);