CoreWLan: wait for scan thread to finish

If the scan thread is running when QCoreWlanEngine is destroyed
it will access stale data and cause a crash.

Task-number: QTBUG-36000
Change-Id: I8cc9e39a3f7d4736da39e8b31f6963db35318f19
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>
Reviewed-by: Peter Hartmann <phartmann@blackberry.com>

src/plugins/bearer/corewlan/qcorewlanengine.mm

@@ -419,6 +419,8 @@ QCoreWlanEngine::QCoreWlanEngine(QObject *parent)
 
 QCoreWlanEngine::~QCoreWlanEngine()
 {
+    scanThread->wait(5000);
+
     while (!foundConfigurations.isEmpty())
         delete foundConfigurations.takeFirst();
     [listener remove];

src/plugins/bearer/corewlan/qcorewlanengine_10_6.mm

@@ -404,6 +404,8 @@ QCoreWlanEngine::QCoreWlanEngine(QObject *parent)
 
 QCoreWlanEngine::~QCoreWlanEngine()
 {
+    scanThread->wait(5000);
+
     while (!foundConfigurations.isEmpty())
         delete foundConfigurations.takeFirst();
     [listener remove];