test plan:
* follow a link to an invitation in the default account
* you should be able to look around the course before accepting
* follow a link to an invitation in a non-default account
* it should immediately accept the invitation or send you through
the registration process if you are not logged in
* enable invitation previews in the settings for the non-default
account
* follow a link to an invitation in that account again
* it should now allow you to preview the course before accepting
Change-Id: I92bde85e0cae9dc4167f5ebd2e32cbbc06aa4242
Reviewed-on: https://gerrit.instructure.com/15636
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Brian Palmer <brianp@instructure.com>
Cody Cutrer