Make service account private key hidden

The service account private key needs to be hidden for safety reasons.
This patch fixes it.

Task: 22886
Story: 1766546

Change-Id: I16929c6de2c442865b2978ae6c18c22b8146f645

magnum/drivers/k8s_fedora_atomic_v1/templates/kubecluster.yaml

@@ -477,12 +477,14 @@ parameters:
 
   kube_service_account_key:
     type: string
+    hidden: true
     description: >
       The signed cert will be used to verify the k8s service account tokens
       during authentication.
 
   kube_service_account_private_key:
     type: string
+    hidden: true
     description: >
       The private key will be used to sign generated k8s service account
       tokens.

magnum/drivers/k8s_fedora_atomic_v1/templates/kubemaster.yaml

@@ -371,12 +371,14 @@ parameters:
 
   kube_service_account_key:
     type: string
+    hidden: true
     description: >
       The signed cert will be used to verify the k8s service account tokens
       during authentication.
 
   kube_service_account_private_key:
     type: string
+    hidden: true
     description: >
       The private key will be used to sign generated k8s service account
       tokens.