runtime: re-enable crash test on NetBSD
runtime: re-enable crash test on NetBSD

Re-enable the crash tests on NetBSD now that the issue has been
identified and fixed.

R=golang-dev, bradfitz
CC=golang-dev
http://codereview.appspot.com/6813100

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