setupapi/tests: Try to delete pre-existing key

[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=25761

Your paranoid android.


=== w1064 (64 bit devinst) ===
devinst.c:1142: Test failed: Unexpected path \\?\root#legacy_bogus#0001#{6a55b5a4-3f65-11db-b704-0011955c2bdb}
devinst.c:1264: Test failed: Expected key to not exist
devinst.c:1370: Test failed: Expected key to not exist