net/http: don't test for goroutine leaks in short mode
net/http: don't test for goroutine leaks in short mode

Too annoying and flaky to debug for now. Later. This
tangent has taken enough time.

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/7863043
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go