Winrt: Fixed compilation of tst_qthread.cpp

Change-Id: I9b3ba920aa1874bbfa7ad499bf2a41c89ae87648
Reviewed-by: Andrew Knight <andrew.knight@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@digia.com>