http: fix racy test with a simpler version
http: fix racy test with a simpler version

This was seen breaking the slow arm5 builder:
http://godashboard.appspot.com/log/ec54ee302a70c07093e8f5c47454b3eb48768b77e1d8cc7943d8951f8b6696be

The test was unnecessarily complex and didn't benefit from
using httptest.Server. That just got in the way.

R=rsc
CC=golang-dev
http://codereview.appspot.com/4439088

tv42/old-go,ssrl/go,ssrl/go,dsriram/golang,dsriram/golang,ssrl/go,ssrl/go,apparentlymart/golang,apparentlymart/golang,pombredanne/go-deleteme,tv42/old-go,gnanderson/go,gnanderson/go,dsriram/golang,apparentlymart/golang,gnanderson/go,dsriram/golang,ssrl/go,tv42/old-go,dsriram/golang,dsriram/golang,apparentlymart/golang,gnanderson/go,tv42/old-go,pombredanne/go-deleteme,ssrl/go,ssrl/go,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,apparentlymart/golang,tv42/old-go,pombredanne/go-deleteme,apparentlymart/golang,gnanderson/go,pombredanne/go-deleteme,gnanderson/go,tv42/old-go,dsriram/golang,gnanderson/go,pombredanne/go-deleteme,apparentlymart/golang