qtd3dservice: Fix bad handle close at shutdown

The control handle event is closed by the service class destructor, and
the worker thread handles are closed by their destructors. So, only
directly close the emulator/phone handles at shutdown.

Change-Id: I03ce660100826f350f742be6e8f6ae1403c6da05
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>