[chromedriver] Actually terminate the suite if failed to quit.

BUG=None
R=kkania@chromium.org

Review URL: https://codereview.chromium.org/32343003

git-svn-id: http://src.chromium.org/svn/trunk/deps/third_party/webdriver@229996 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
3 files changed