Remove SecurityContextDeny API plugin

This is no longer recommended for use since K8s 1.2:
http://kubernetes.io/docs/admin/admission-controllers/#is-there-a-recommended-set-of-plug-ins-to-use

roles/kubernetes/master/templates/manifests/kube-apiserver.manifest.j2

@@ -15,7 +15,7 @@ spec:
     - --etcd-servers={{ etcd_access_endpoint }}
     - --insecure-bind-address={{ kube_apiserver_insecure_bind_address }}
     - --apiserver-count={{ kube_apiserver_count }}
-    - --admission-control=NamespaceLifecycle,NamespaceExists,LimitRanger,SecurityContextDeny,ServiceAccount,ResourceQuota
+    - --admission-control=NamespaceLifecycle,NamespaceExists,LimitRanger,ServiceAccount,ResourceQuota
     - --service-cluster-ip-range={{ kube_service_addresses }}
     - --client-ca-file={{ kube_cert_dir }}/ca.pem
     - --basic-auth-file={{ kube_users_dir }}/known_users.csv