Fall back to English if user has bogus locale set
Fall back to English if user has bogus locale set

Fixes: CORE-1473

Test plan:
* go to /accounts/x/users
* do something where your ENV.LOCALE is not something we support (like
  “en-US”. (I honestly don’t know how you would get into this state but
  The thing I did is put a breakpoint in the top of the vendor.js file
  So I could manually set it to something like: 
  `ENV.LOCALE =“en-US”
* load the page, it should load
* click on the pencil to edit a user’s details, the list of <options>
  For the timezone select should appear and should use the English 
  defaults

Change-Id: I7c1612fbc115eb5a598e590a2db3fd4e61bad93c
Reviewed-on: https://gerrit.instructure.com/154728
Tested-by: Jenkins
Reviewed-by: Clay Diffrient <9dff2e5c98626d20d2848250c411e8009465bb87@instructure.com>
Product-Review: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>
QA-Review: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>

instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,djbender/canvas-lms