Add periodic timestamp logging. (#4858)
Add periodic timestamp logging. (#4858)

Fixes #4827
bmw/boulder,jsha/boulder,bmw/boulder,jcjones/boulder,jcjones/boulder,jcjones/boulder,letsencrypt/boulder,jsha/boulder,letsencrypt/boulder,bmw/boulder,jsha/boulder,letsencrypt/boulder,jcjones/boulder