mmdevapi/tests: Fix wrong buffer unit and memory leaks.

Hi,
> * nBlockAlign is wrong since data is counted in frames, not bytes.
> I forgot to comment that I introduced the 10x multiplicator to
> convince myself that GetData accepts buffer sizes larger than the
> default 10ms chunk returned by GetDevicePeriod.  That is reasonable, but
> not guaranteed when I read MSDN (the API would work with small buffers too).

Regards,
	Jörg Höhle