dsound: fix a few failing tests and a crash on 2008

[Paul Vriens]

Jeff Zaroyko wrote:
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I found more or less the same thing for Vista a few days ago. Doing a 
IDirectSoundBuffer_Release sets the reference counter to zero but doesn't clear 
secondary. Is this something worthwhile to add a comment for (or a test)? It 
does seem important as it's a change of behavior starting with Vista?

-- 
Cheers,

Paul.