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

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang