http/Body: re-add Consumed() call
http/Body: re-add Consumed() call

This was not Istream::Consumed(), but HttpBodyReader::Consumed().  How
confusing!

CM4all/beng-proxy,CM4all/beng-proxy,CM4all/beng-proxy,CM4all/beng-proxy,CM4all/beng-proxy,CM4all/beng-proxy