Allow LTIs to load with a custom template
Allow LTIs to load with a custom template

This is a temporary fix until a permanent one trickles down from
Instructure.

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