Don't crash at runtime with when relaying a signal.
Don't crash at runtime with when relaying a signal.

We have this function called qDBusInterfaceFromMetaObject that
calculates the interface name from a given meta object. There's no
need to duplicate the code here (and not do it right).

All tests still pss.

Task-number: 236955
Reviewed-by: Trust Me

igor-sfdc/qt-wk,radekp/qt,KDE/qt,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,radekp/qt,KDE/qt,pruiz/wkhtmltopdf-qt,KDE/qt,radekp/qt,radekp/qt,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,RLovelett/qt,radekp/qt,pruiz/wkhtmltopdf-qt,KDE/qt,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,igor-sfdc/qt-wk,KDE/qt,RLovelett/qt,RLovelett/qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,radekp/qt,RLovelett/qt,KDE/qt,KDE/qt,RLovelett/qt,radekp/qt,igor-sfdc/qt-wk,radekp/qt,RLovelett/qt,RLovelett/qt,pruiz/wkhtmltopdf-qt,RLovelett/qt,igor-sfdc/qt-wk,RLovelett/qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,RLovelett/qt,RLovelett/qt,igor-sfdc/qt-wk,radekp/qt,radekp/qt,KDE/qt,pruiz/wkhtmltopdf-qt