Fix for TestQuestions.test_that_posting_question_works

This test is failing because the "staging site banner" is blocking the "<code>none_of_these_solve_my_problem_button</code>", so I added this walk-around method to close the banner first.
This is a screenshot http://qa-selenium.mv.mozilla.com:8080/job/sumo.fft.saucelabs/1425/HTML_Report/debug/tests_desktop_test_questions_TestQuestions/test_that_posting_question_works/screenshot.png