[dinput/tests] Fix a few intermittent test failures

[Vitaliy Margolen]

Paul Vriens wrote:
> Hi,
> 
> For some reason SetFocus(0) doesn't always have the desired effect of
> losing the input for this test. Creating a temp window does.
> 
> This almost always happened on my Win98 (VMware) box, but
> test.winehq.org also shows some real boxes (including a WinME and XP
> one) that have this same issue.
Could be because some previous tests kill/crash explorer.

Creating new window might work, as long as you pump messages to be sure the
window is created. Not really required but nice to get things in synch.
Other then that don't have any issues.

Vitaliy.