Do not block waiting for chromedriver to start up (#46126)
This would save approximately 0.5 second on each test runner restarts.
And this should not cause a problem as another connection to the
webdriver will be made to init the session, which also happens during
initialization stage.
https://github.com/web-platform-tests/wpt/blob/master/tools/wptrunner/wptrunner/testrunner.py#L93