(#7501)   Split cmd_drain_policies into four different tests, part 3.  Add test_job_policy_on_backfill.
(#7501)   Split cmd_drain_policies into four different tests, part 3.  Add test_job_policy_on_backfill.

htcondor/htcondor,htcondor/htcondor,htcondor/htcondor,htcondor/htcondor,htcondor/htcondor,htcondor/htcondor,htcondor/htcondor,htcondor/htcondor