Resolve "Tape server querying DB at very high rate"

Summary

This MR is to fix this specific cause of high DB queries: #155 (comment 6266313)

Requires manual tests in pre-production

NO. The high query rate is only evidenced when there are many tape servers and a high rate of retrieve requests. Best way to test this is in production:

1. Get an updated query rate from Nilo
2. Deploy the version of CTA containing this fix
3. Get a new query rate and it should hopefully be much lower

References

Closes #155 (closed)