Do not emit warning in logs for 3xx HTTP status codes
We currently log HTTP requests returning 304 status codes as warnings, which does not make sense to me, it is not harmful.
Ex: [2019-07-07T09:04:52.407] [WARN] HTTP - GET /themes.json - 304 (57 ms)
This MR sets the log level to info for status codes from 301 to 309. I kept "multiple choices" and "too many redirects" as warnings.