Export ocsp_status_staleness for 15, 18, 21, and 24hr buckets (#5627)
Export ocsp_status_staleness for 15, 18, 21, and 24hr buckets (#5627)

Fixes #5626
jcjones/boulder,jcjones/boulder,letsencrypt/boulder,jcjones/boulder,jsha/boulder,letsencrypt/boulder,jsha/boulder,jsha/boulder,jcjones/boulder,letsencrypt/boulder