msi/tests: Fix MsiApplyMultiplePatches tests on Windows.

[Nicolas Le Cam]

Hi,

This patch fixes recent MsiApplyMultiplePatches tests on Windows
platforms.
Tested on Win2k and WinXP.

Testing it on a network drive revealed new errors, so I've updated the
test accordingly.

Fixing it will need a little more time as I need to add tests for
MsiApplyPatch before to see if it behaves the same, but it seems space
trimming logic is the culprit here.

--
Nicolas Le Cam