Fix for the test_connect_to_wifi_via_settings_app fail

The problem was the wait_for_element_present, it was not waiting enough for the element to be visible.
http://qa-selenium.mv.mozilla.com:8080/job/b2g.unagi.gaia.v1-train.ui/564/testReport/junit/%28root%29/TestSettingsWifi/test_connect_to_wifi_via_settings_app/