net: do not set SO_REUSEADDR for windows
net: do not set SO_REUSEADDR for windows

Fixes issue 2307.

R=golang-dev, mikioh.mikioh
CC=golang-dev
http://codereview.appspot.com/5306049

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