Add kubernetes-test.tar.gz

Add test artifacts to the build. This lets you do:

tar -xzf kubernetes.tar.gz
tar -xzf kubernetes-test.tar.gz
cd kubernetes
go run ./hack/e2e.go -up -test -down

without having a git checkout.
Heh -- golang.sh is looking more and more like the wrong place to put this stuff.  Not necessary to fix right now.