wintrust/tests: Fix test for pfnAddSgnr2Chain.

[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=25506

Your paranoid android.


=== w864 (32 bit softpub) ===
softpub: unhandled exception c0000005 at 77723ED2

=== w1064 (32 bit softpub) ===
softpub: unhandled exception c0000005 at 768AC81B

=== w864 (64 bit softpub) ===
softpub: unhandled exception c0000005 at 00007FFB7AFF266C

=== w1064 (64 bit softpub) ===
softpub.c:254: Test failed: Expected S_OK, got 00000001
softpub.c:257: Test failed: Expected S_OK, got 00000001
softpub: unhandled exception c0000005 at 00007FFC77A79A5D