Hotfix/lms a11y

a11y hotfixes for:
1) be able to escape the forgot password modal by pressing "ESC"
https://edx-wiki.atlassian.net/browse/LMS-1166

2) fix typo at https://github.com/edx/edx-platform/compare/release...hotfix/lms-a11y?expand=1#L1L64
https://edx-wiki.atlassian.net/browse/LMS-583

3) manage focus within help modal once "submit" has been hit
https://edx-wiki.atlassian.net/browse/LMS-581

@talbs @singingwolfboy 

@gwprice , coming your way