update helm/tiller to v2.7.2 -- security bugfix (#1986)

roles/download/defaults/main.yml

@@ -117,14 +117,11 @@ kibana_version: "v4.6.1"
 kibana_image_repo: "gcr.io/google_containers/kibana"
 kibana_image_tag: "{{ kibana_version }}"
 
-# Intentionally missing 'v' prefix. See https://github.com/lachie83/k8s-helm/issues/20
-helm_version: "2.7.0"
+helm_version: "v2.7.2"
 helm_image_repo: "lachlanevenson/k8s-helm"
 helm_image_tag: "{{ helm_version }}"
-# Fix when helm_version is fixed
-tiller_version: "v2.7.0"
 tiller_image_repo: "gcr.io/kubernetes-helm/tiller"
-tiller_image_tag: "{{ tiller_version }}"
+tiller_image_tag: "{{ helm_version }}"
 
 downloads:
   netcheck_server: