fix reset-course-content on canvas_net courses without profiles

default course profiles are invalid in canvas_net accounts
due to additional fields with presence validators, so they
can't be assigned via `Course#profile=`

test plan:
 - "reset course content" button in course settings should function
   on a course in a canvas_net account that does not have a profile

fixes CNVS-17153

Change-Id: Id20289aed76d5ec3effbad96110c974682376589
Reviewed-on: https://gerrit.instructure.com/45234
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: James Williams  <jamesw@instructure.com>
QA-Review: Jahnavi Yetukuri <jyetukuri@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>