Remove Test users in Prod application instances from ORG Billable counts

[mkdir-washington-edu]

Test users (e.g. when an instructor clicks "Student Preview" in their LMS and launches a Hypothesis assignment) are created periodically, but should not be counted as Billable users.

In some LMSs test users get a display name like "Test Student" and may get a role like http://purl.imsglobal.org/vocab/lti/system/person#TestUser. In other cases, the test user gets the #Learner role and uses the same name as the instructor. We think they should not, however, appear on the course rosters we are beginning to get.

We should find and filter Test users like this out of our Billable user counts.