cache 'everyone' search result in new conversations

fixes CNVS-12865

test plan
- as a teacher in new conversations, compose a new message
- select 'all in course' from the people picker drop down
- ensure that 'all in course' can be selected
- ensure that the message can be sent and is delivered to all
 users in the course

Change-Id: I6f2e0ad30ca2a09e52b4b5b764f3c21ecc0628f0
Reviewed-on: https://gerrit.instructure.com/34291
Tested-by: Jenkins <[email protected]>
Reviewed-by: Jon Willesen <[email protected]>
QA-Review: Steven Shepherd <[email protected]>
Product-Review: Joel Hough <[email protected]>

app/coffeescripts/views/conversations/AutocompleteView.coffee

@@ -271,9 +271,9 @@ define [
     # Returns nothing.
     _onSearchResultLoad: =>
       @cache[@currentUrl] = @resultCollection.toJSON()
-      @resultCollection.each @_addToModelCache
       _.extend(@permissions, @_getPermissions())
       @_addEveryoneResult(@resultCollection) unless @excludeAll or !@_canSendToAll()
+      @resultCollection.each @_addToModelCache
       shouldDrawResults = @resultCollection.length
       isFinished        = !@nextRequest
       @_addBackResult(@resultCollection)