Rollback helm version to 2.7.2

The update to helm 2.8.0 resulted in issues with releases not
registering as ready before timing out. This rolls the version back
until those issues are addressed

Change-Id: Id58f85f150054d82c047bd360258ebe9e571360f

tiller/values.yaml

@@ -25,7 +25,7 @@ release_group: null
 
 images:
   tags:
-    tiller: gcr.io/kubernetes-helm/tiller:v2.8.0
+    tiller: gcr.io/kubernetes-helm/tiller:v2.7.2
     dep_check: quay.io/stackanetes/kubernetes-entrypoint:v0.2.1
     image_repo_sync: docker.io/docker:17.07.0
   pull_policy: IfNotPresent

tools/gate/playbooks/vars.yaml

@@ -14,7 +14,7 @@
 
 version:
   kubernetes: v1.9.2
-  helm: v2.8.0
+  helm: v2.7.2
   cni: v0.6.0
 
 images: