net: disable SIO_UDP_CONNRESET behavior on windows.

Fixes issue 5834.

LGTM=alex.brainman
R=golang-codereviews, bradfitz, alex.brainman, mikioh.mikioh, in60jp, iant
CC=golang-codereviews
https://codereview.appspot.com/149510043

Committer: Alex Brainman <alex.brainman@gmail.com>