Fix lettuce tests for Xenial compatibility and newer Chrome version.

(cherry-picked from c3887b0b)

Properly wait for LTI stub's buttons to render

(cherry-picked from c58e5142)

Workaround for intermittent chromedriver hangs upon start.

(cherry-picked from 840efb23)

Refactor click since it was resulting in timeout errors; use correct id for one of the LTI stub's buttons.

(cherry-picked from 452a1f1f)

Solve open sans quotation issue with tests.

(cherry-picked from 0e7e9468)

Fixes for chrome reliability in selenium.

Fix for rendering timing issue. See https://bugs.chromium.org/p/chromedriver/issues/detail?id=1552

(cherry-picked from e7b0c28d)

Multi-thread stub servers.

(cherry-picked from 0e596dd5)

Lettuce-on-Xenial CMS fix. Iterate through a list to avoid quotation string confusion.

Also change some selenium settings (they were not necessary at this time).

(cherry-picked from c0dd2b87)