fix testcase: wait on all threads only if execution is done multithreaded

VectoCore/VectoCoreTest/Integration/Declaration/HeavyLorry/HeavyLorrySimulation.cs

@@ -69,7 +69,9 @@ public class HeavyLorrySimulation
 		PrintRuns(jobContainer, null);
 		
 		jobContainer.Execute(multiThreaded);
-		jobContainer.WaitFinished();
+		if (multiThreaded) {
+			jobContainer.WaitFinished();
+		}
 		Assert.IsTrue(jobContainer.AllCompleted);
 		Assert.IsTrue(jobContainer.Runs.TrueForAll(runEntry => runEntry.Success));
 		PrintRuns(jobContainer, fileWriter);