http: cleaned up HEAD request method.
http: cleaned up HEAD request method.

Removed a redefinition of the request URL which is never used and
redundant checking of the return value from send().

R=golang-dev, adg
CC=golang-dev
http://codereview.appspot.com/4184061

Committer: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>

wesolows/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang,wesolows/golang,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,wesolows/golang,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,wesolows/golang-old,wesolows/golang-old