The x/net package is currently broken for Go 1.9 (#19051) so
I am unable to use trybots for x/net/http2.

This disables the tests for the broken stuff and makes things compile
at least, so x/net trybots aren't broken for others.

Updates golang/go#19051

Change-Id: I67401d7ad32d855e99a417545328eb4e803287cc
Reviewed-on: https://go-review.googlesource.com/37401
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matt Layher <mdlayher@gmail.com>
Reviewed-by: Martin Möhrmann <moehrmann@google.com>