winmm/tests: Change the current directory to a place that will be writable.

[Francois Gouget]

On Mon, 24 Feb 2014, Marvin wrote:
[...]
> === w8 (32 bit mci) ===
> mci.c:1123: Test failed: got 0001 instead of MCI_NOTIFY_xyz 0004 from command play (aborted by close)

Not related to my patch.


-- 
Francois Gouget <fgouget at codeweavers.com>