Revert "Try to open page in setUp."

This reverts commit 37e58a89612e2b845813ca953a7beaeb0552455b.

It needs to be done with existing session.
Workaround for Selenium tests with coverage

The phpunit-selenium tries to set cookie just after opening Selenium
session, what fails (at least with Chrome) as the browser is currently
pointing to data: URL and not our application one. So we need to set URL
just as the Selenium session is opened.

Signed-off-by: Michal Čihař <michal@cihar.com>