CppTools: Fix test_modelmanager_extraeditorsupport_uiFiles

The test was broken since the QmakeProject was changed to work
asynchronously.

FAIL!  : CppTools::Internal::CppToolsPlugin::test_modelmanager_extraeditorsupport_uiFiles() Compared values are not the same
   Actual   (workingCopy.size()): 1
   Expected (2)                 : 2

Change-Id: I6f7d05fb70af3def5fc371a9783b606309686e32
Reviewed-by: Christian Stenger <christian.stenger@theqtcompany.com>

src/plugins/coreplugin/testdatadir.cpp

@@ -59,6 +59,11 @@ QString TestDataDir::file(const QString &fileName) const
     return directory() + fileName;
 }
 
+QString TestDataDir::path() const
+{
+    return m_directory;
+}
+
 QString TestDataDir::directory(const QString &subdir, bool clean) const
 {
     QString path = m_directory;