Split deploy steps in separate playbooks: part1 (#3451)

* Fix bootstrap_os/ubuntu idempotency

* Update bastion role

* move container_engine in sub-roles

* requires ansible 2.5

* ubuntu18 as first CI job

tests/files/gce_centos-weave-kubeadm-sep.yml

@@ -0,0 +1,15 @@
+# Instance settings
+cloud_image_family: centos-7
+cloud_machine_type: "n1-standard-1"
+cloud_region: us-central1-b
+mode: ha
+
+startup_script: ""
+
+# Deployment settings
+kube_network_plugin: weave
+kubeadm_enabled: true
+deploy_netchecker: true
+kubernetes_audit: true
+kubedns_min_replicas: 1
+cloud_provider: gce