QtPrintSupport: cleanup CUPS tmp files

Set fd so that it gets closed in QPdfPrintEnginePrivate::closePrintDevice()

Task-number: QTBUG-14724

Change-Id: Ic9c02c92b07ece92911d7bc3eac79689b4864253
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>

src/plugins/printsupport/cups/qcupsprintengine.cpp

@@ -180,6 +180,7 @@ bool QCupsPrintEnginePrivate::openPrintDevice()
         cupsTempFile = ret.second;
         outDevice = new QFile();
         static_cast<QFile *>(outDevice)->open(ret.first, QIODevice::WriteOnly);
+        fd = ret.first;
     }
 
     return true;