don't re-preload overrides for every role
don't re-preload overrides for every role

refs FOO-1019

Change-Id: Iec17dcbfae1d3c56a29ab7bffd7aaa248b069187
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/270071
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: August Thornton <9adc7a1161ddf32ff608de792a7e50179545f026@instructure.com>
QA-Review: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>
Product-Review: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>

sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms