fix erb js_env with template streaming enabled
fix erb js_env with template streaming enabled

test plan:
- enable template streaming by adding this
  to config/dynamic_settings.yml:

  private:
    canvas:
      enable_template_streaming: true

- go to the course modules page
- edit a module requirement that some students have
  already fulfilled
- at the prompt, click "Relock modules"
- you should not get an AJAX error

fast test plan:
- open the javascript console and verify ENV.COURSE_ID is set

flag=none
fixes LA-309

Change-Id: Iac8a9577e9304238380a02222eeaf89729869d7c
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/218843
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Tested-by: Jenkins
Reviewed-by: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>
QA-Review: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>
Product-Review: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>

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