Set things up for logging in positioning test application

Change-Id: I3f44e1a1d5022c00db149b2ba23d4dd91d3b1f1a
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>

tests/applications/positioning_backend/main.cpp

@@ -31,8 +31,11 @@
 
 #include <QApplication>
 #include <QtWidgets>
+#include <QLoggingCategory>
+
 int main(int argc, char *argv[])
 {
+    //QLoggingCategory::setFilterRules("qt.positioning.*=true");
     QApplication a(argc, argv);
 
     LogWidget *log = new LogWidget;