Prevent harmless warnings when using VDPAU with Nouveau driver.

nouveau's vdpau drivers returns an error when fed invalid data while the nvidia's driver just tag along.

Those errors were harmless, but made the logs a bit verbose during playback startup.
The call to DrawBitmap in CreateOutputSurface seems to have been a legacy of the original VDPAU painter which was using a single surface to draw everything.