Optimise windows cert fetching and fix test case.

Optimise windows cert fetching and fix test case.

If we're not going to verify the peer, or we know in advance that
windows won't have a CA root then don't ask it to verify the
certificate chain.
The test case started failing in CI when the windows cert fetcher
was integrated due to timing change. I've relaxed the timing
requirement of the test to avoid it being unstable.

Task-number: QTBUG-24827
Change-Id: I694f193f7d96962667f00aa01b9483b326e3e054
Reviewed-by: Martin Petersson <Martin.Petersson@nokia.com>