Update Kubernetes to v1.9.0 (#2100)

Update checksum for kubeadm
Use v1.9.0 kubeadm params
Include hash of ca.crt for kubeadm join
Update tag for testing upgrades
Add workaround for testing upgrades
Remove scale CI scenarios because of slow inventory parsing
in ansible 2.4.x.

Change region for tests to us-central1 to
improve ansible performance