Accept 403 responses in the uproxy.org 404 integration test.
Accept 403 responses in the uproxy.org 404 integration test.

This started failing after we started using cloudflare for
uproxy.org

jpevarnek/uproxy,jpevarnek/uproxy,jpevarnek/uproxy,uProxy/uproxy,uProxy/uproxy,uProxy/uproxy,jpevarnek/uproxy,uProxy/uproxy,jpevarnek/uproxy,uProxy/uproxy