CLC-4240 Reduce number of SLOW warnings in log files

… but improve our coverage of slow responses from CalCentral. This should make the morning production audit emails easier to read.

https://jira.ets.berkeley.edu/jira/browse/CLC-4240

Thanks, @christianv, for the reminder. The worrisome queries are for our own PostgreSQL DB. I've brought their wildly varying times up to IST in the past but I might as well ping them again. On the Oracle side, they're mostly Sakai checks and huge collections of roster photos, and haven't seemed to be causing big problems IRL.