test_FindFirstChangeNotification: Handle case when directory already exists

[Uwe Bonnes]

from some aborted run, directory c:/windows/temp/testFileChangeNotification
existed already on my system and this caused kernel32/test/change.c test to abort. 

If the directory already exists, try to find to append some character until
the directory for the new name doesn't exist.

-- 
Uwe Bonnes                bon at elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt
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