Don't ask for passwords in kfilewidgettest

Summary:
Changed the test to check if the root urls are right for _k_enterUrl.
Can check any schema because the test does not run them.

Test Plan: The test passes with the changes done in https://phabricator.kde.org/D13674, they fail otherwise.

Reviewers: dfaure, Frameworks

Reviewed By: dfaure

Subscribers: kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D13939