The function that sets test case metadata is actually named ${tc}_head
rather than ${tc}, so add the suffix.
While we're here, hook the tests up to the infrastructure so that they
do get run.
Sponsored by: Klara, Inc.
Also add a test to ensure that it is working correctly.
Submitted by: ota_j.email.ne.jp
Reviewed by: mckusick
Differential Revision: https://reviews.freebsd.org/D34012