Treat request URL as CDATA so query string params don't result in invalid XML

If the request url reported contains invalid XML characters, we get

Nokog​iri::​XML::​Synta​xErro​r: En​tityR​ef: e​xpect​ing '​;'

This is similar to 6c30142fb0018dc85bedded605b3eea4f49d0c42