topgun/k8s: default k8s-Engine to GKE
topgun/k8s: default k8s-Engine to GKE

Signed-off-by: Ciro S. Costa <4f5054ab2db051d03adf9068233a850c82b24437@pivotal.io>
Co-authored-by: Bishoy Youssef <9b4d1ba1708a9b42aa1e22343aa1f23ecf97ab43@pivotal.io>

concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse