net: reduce dial tests on netbsd
net: reduce dial tests on netbsd

Add NetBSD to the list of operating systems that have a reduced set
of dial tests.

R=golang-dev, r
CC=golang-dev
http://codereview.appspot.com/6208083

wesolows/golang-old,wesolows/golang,wesolows/golang-old,wesolows/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang,wesolows/golang-old,wesolows/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang-old,wesolows/golang,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang,wesolows/golang,firebitsbr/golang-old