CppEditor/CppTools: Tests: Fix potential race condition

...when updating the code model.

Change-Id: Ifc55b7d0bb795b9cfd72465990991bc2cc907846
Reviewed-by: Christian Stenger <christian.stenger@digia.com>
Reviewed-by: Erik Verbruggen <erik.verbruggen@digia.com>

src/plugins/cpptools/modelmanagertesthelper.h

@@ -80,6 +80,7 @@ public:
 
     Project *createProject(const QString &name);
 
+    void resetRefreshedSourceFiles();
     QStringList waitForRefreshedSourceFiles();
     void waitForFinishedGc();