util/stop: Update logging
util/stop: Update logging

Specifically, when debugging unit test logs, knowing when stop was called really
helps isolate where the error occurred.

petermattis/cockroach,veteranlu/cockroach,paperstreet/cockroach,veteranlu/cockroach,petermattis/cockroach,vaibhavarora/cockroach,glycerine/cockroach,maxlang/cockroach,vaibhavarora/cockroach,paperstreet/cockroach,veteranlu/cockroach,maxlang/cockroach,vaibhavarora/cockroach,petermattis/cockroach,veteranlu/cockroach,paperstreet/cockroach,veteranlu/cockroach,vaibhavarora/cockroach,maxlang/cockroach,paperstreet/cockroach,paperstreet/cockroach,veteranlu/cockroach,maxlang/cockroach,veteranlu/cockroach,maxlang/cockroach,veteranlu/cockroach,cockroachdb/cockroach,petermattis/cockroach,cockroachdb/cockroach,maxlang/cockroach,paperstreet/cockroach,maxlang/cockroach,petermattis/cockroach,vaibhavarora/cockroach,cockroachdb/cockroach,maxlang/cockroach,glycerine/cockroach,glycerine/cockroach,vaibhavarora/cockroach,paperstreet/cockroach,glycerine/cockroach,cockroachdb/cockroach,cockroachdb/cockroach,petermattis/cockroach,petermattis/cockroach,glycerine/cockroach,glycerine/cockroach,vaibhavarora/cockroach,vaibhavarora/cockroach,paperstreet/cockroach,cockroachdb/cockroach,glycerine/cockroach,petermattis/cockroach,glycerine/cockroach,cockroachdb/cockroach,cockroachdb/cockroach