explicitly save course after migration for rails 3 compatibility

Change-Id: I3b2337e88c0b4717d76cd6735a82be0ededa0950
Reviewed-on: https://gerrit.instructure.com/29041
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
QA-Review: James Williams  <jamesw@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>