Bug 1006226 - [marketplace-tests-gaia] Address intermittent failure of test_marketplace_feedback_login by improving waits

Adhoc running at http://selenium.qa.mtv2.mozilla.com:8080/view/B2G%20Hamachi/job/b2g.hamachi.mozilla-b2g28_v1_3.v1.3.marketplace.adhoc/21/console