Improve information logged in log_request_end()

With this change, no longer will we log:
I, [2014-11-11T17:01:10.138555 #33103]  INFO -- : Completed in 1179ms | 200 | - bytes

Instead, we will log:
I, [2014-11-11T17:21:18.903014 #34801]  INFO -- : Completed in 1209ms | 200 OK | 3156 bytes