Update Kubernetes version
Update Kubernetes version

As per UCP 3.0.6 release, UCP ships with Kubernetes 1.8.15.
londoncalling/docker.github.io,londoncalling/docker.github.io,londoncalling/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io,londoncalling/docker.github.io,docker/docker.github.io,docker/docker.github.io,londoncalling/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io