Check database left overs after periodic test cleanup

[bwbroersma]

@aequitas found out database_cleanup does not seem to cleanup all reports, e.g. check:

SELECT domain, COUNT(*) FROM checks_domaintesttls GROUP BY domain ORDER BY COUNT(*) DESC LIMIT 10;
SELECT domain, COUNT(*) FROM checks_domaintestreport GROUP BY domain ORDER BY COUNT(*) DESC LIMIT 10;

and see some testing domain endpoints listed.

Maybe only on dev1, maybe a broader problem.