qedit/tests: Improve test messages

[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
http://testbot.winehq.org/JobDetails.pl?Key=25328

Your paranoid android.


=== W2KPROSP4 (32 bit mediadet) ===
mediadet.c:149: Test failed: CoCreateInstance failed: 80040154
mediadet: unhandled exception c0000005 at 00401588

=== W2K8SE (32 bit mediadet) ===
mediadet.c:149: Test failed: CoCreateInstance failed: 80040154
mediadet: unhandled exception c0000005 at 00401588