CoreCon: mark destructor as virtual

This was causing COM to not get uninitialized and resulted in
winrtrunner hanging.

Change-Id: Ie3e409a43f2cb41f28ef6975d81c68996554861f
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>

src/shared/corecon/corecon.cpp

@@ -155,7 +155,7 @@ protected:
         if (FAILED(hr))
             qCDebug(lcCoreCon) << "Failed to initialize COM.";
     }
-    ~ComInitializer()
+    virtual ~ComInitializer()
     {
         if (SUCCEEDED(hr))
             CoUninitialize();