shell32/tests: Reset "current directory" of current process.

[Marvin]

Hi,

While running your changed tests on Windows, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?
Full results can be found at
https://testbot.winehq.org/JobDetails.pl?Key=20931

Your paranoid android.


=== w1064 (32 bit shlfolder) ===
shlfolder.c:1591: Test failed: IShellFolder_GetDisplayNameOf(NULL) failed! hr = 80070057