Add new addon Istio (#1744)

.gitlab-ci.yml

inventory/group_vars/k8s-cluster.yml

roles/download/defaults/main.yml

roles/kubernetes-apps/istio/defaults/main.yml

roles/kubernetes-apps/istio/meta/main.yml

roles/kubernetes-apps/istio/tasks/main.yml

.../kubernetes-apps/istio/templates/istio-initializer.yml.j2

roles/kubernetes-apps/istio/templates/istio.yml.j2

roles/kubernetes-apps/meta/main.yml

roles/kubernetes/master/defaults/main.yml

...tes/master/templates/manifests/kube-apiserver.manifest.j2

roles/kubespray-defaults/defaults/main.yaml