runtime: deadlock tests now work with GOMAXPROCS>1 Fixes issue 4826.
runtime: deadlock tests now work with GOMAXPROCS>1
Fixes issue 4826.

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/7434046
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go