fix i18n scope inference in views, fixes CNVS-14815

this broke with the rails 3 upgrade

1. `render :collection` was not getting the correct scope (it just kept
   the parent's)
2. `render :partial` was not getting the correct scope if the partial was
   in the same directory as the main template, e.g.
   `render :partial => 'courses_right_side'` would have courses_right_side
   as its scope instead of the correct accounts.courses_right_side

test plan:
1. run canvas with RAILS_LOAD_ALL_LOCALES=true
2. change your language from english
3. go to the accounts show page
4. behold the translated strings (in particular the right sidebar, and the
   various counts/stats for each course in the main content area)
5. confirm that i18n is working elsewhere
6. note: if you're regression testing i18n everywhere, you'll also need to
   compile assets and run canvas with USE_OPTIMIZED_JS=true to get
   translations working in javascript land. that's technically not needed
   to verify this commit, but it'll eliminate any false positives

Change-Id: I594a403f7d4611e74c76ff05e9fb7542c6d3a80d
Reviewed-on: https://gerrit.instructure.com/39399
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Amber Taniuchi <amber@instructure.com>
Product-Review: Matt Fairbourn <mfairbourn@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>