Avoid creating null parameters

Change-Id: I63c4498560fdc5dfeb6ffa3e29b6620432994ce1
Related-To: PROD-36193
diff --git a/nova/meta/grafana.yml b/nova/meta/grafana.yml
index 0ed0b1a..8f233a4 100644
--- a/nova/meta/grafana.yml
+++ b/nova/meta/grafana.yml
@@ -1,11 +1,9 @@
 {%- from "nova/map.jinja" import controller, compute with context %}
 parameters:
-  {%- if compute is defined and compute.get('enabled', False) and compute.get('ceph', {}).get('ephemeral', False) %}
-  nova_compute_ceph_ephemeral: True
-  {%- endif %}
-  {%- if controller is defined and controller.get('version',{}) in ["juno", "kilo", "liberty", "mitaka"] %}
-  nova_cert_enabled: True
-  {%- endif %}
+  {%- set nova_compute_ceph_ephemeral = compute is defined and compute.get('enabled', False) and compute.get('ceph', {}).get('ephemeral', False) %}
+  nova_compute_ceph_ephemeral: {{ nova_compute_ceph_ephemeral }}
+  {%- set nova_cert_enabled = controller is defined and controller.get('version',{}) in ["juno", "kilo", "liberty", "mitaka"] %}
+  nova_cert_enabled: {{ nova_cert_enabled }}
 dashboard:
 {%- if pillar.get('fluentd', {}).get('agent', {}).get('enabled', False) %}
   nova_overview_prometheus: