The issue itself is not really worth fixing (the very first request
being supposed to have a different proxy than any of the other
following requests before a session has been initiated), but we can
at least make the test pass when it is run alone.
Task-number: QTBUG-63134
Change-Id: I6c7df5c5653541031811e6bff562572061afae0f
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>