Temporarily disable CAPA problem "Check" button.

- update appropriate jasmine tests so that stubbed $postWithPrefix
respects a subset of jQuery promise API.
- add customization for checking state.
- display checking state while button is disabled.
- ensure checking state lasts for at least a second.
Convert first batch of lettuce video tests to bok-choy.
Merge pull request #2440 from glowe/prevent-duplicate-checks

Temporarily disable CAPA problem "Check" button.
Disable discussion service setting for lettuce tests
Merge pull request #3217 from edx/ammar/convert-lettuce-video-tests-to-bok-choy

Convert lettuce video tests to bok choy
Merge pull request #3305 from edx/zoldak/no-lettuce-with-discussion

Disable discussion service setting for lettuce tests
Support for Duplicate and Delete of XBlock Container Leaves (disabled under Feature Flag).
fix for fuzzy prompt on container page