Prevent some duplicate redis fetches
Prevent some duplicate redis fetches

Without this, on a teacher request to the dashboard page I get a bunch
Of duplicate 
`Redis (0.481ms) get shard_xxx:users/x/has_student_enrollment`
Requests (and others for the other methods here too)

I know that it will be a redis cache hit but it still actually has
To hit redis and the network between app server and redis

test plan:
* nothing actually changes
* you should just see less "has_student_enrollment" redis lookups in
  the rails log for a request to the dashboard page

Change-Id: I1199a877904b45af27e56a78229075366897ec9a
Reviewed-on: https://gerrit.instructure.com/195508
Tested-by: Jenkins
Reviewed-by: Rob Orton <7e09c9d3e96378bf549fc283fd6e1e5b7014cc33@instructure.com>
QA-Review: Rob Orton <7e09c9d3e96378bf549fc283fd6e1e5b7014cc33@instructure.com>
Product-Review: Rob Orton <7e09c9d3e96378bf549fc283fd6e1e5b7014cc33@instructure.com>

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