Connection: Don't log request/response with INFO

It is not a good idea to log all the request and response information as INFO. One reason is we generate a ton of data with no need in a production environment. But much more important we would log ArangoDB authentication details.

This is somewhat related to [this issue in Guacamole][1].

[1]: https://github.com/triAGENS/guacamole/issues/34