[PATCH] mf/tests: Avoid cast from COM object to interface

[Marvin]

Hi,

While running your changed tests, 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=96350

Your paranoid android.


=== w8adm (32 bit report) ===

mf:
mf.c:4243: Test failed: Unexpected hr 0x800401f0.