http: do not listen on 0.0.0.0 during test
http: do not listen on 0.0.0.0 during test

Quiets the pop-up boxes on OS X.

R=bradfitzgo, r2
CC=golang-dev
http://codereview.appspot.com/4387042

tav/go,tav/go,tav/go,tav/go,tav/go,tav/go,tav/go