spec: intermittent selenium spec fixes

Change-Id: I22f9bac01be93563421df21a8c837a059696f5bc
Reviewed-on: https://gerrit.instructure.com/37806
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Bryan Madsen <bryan@instructure.com>
Product-Review: Bryan Madsen <bryan@instructure.com>
QA-Review: Bryan Madsen <bryan@instructure.com>