ceilometer_agent_notification: disable-panko.yaml

ceilometer-agent-notification.yaml updated the
kolla_config section in template file to include
nothing related to panko when disable-panko env file is passed.

Closes-Bug: #1824840

Change-Id: Ia71e80c84449209653609c911fef4cb3cdce5b5c
(cherry picked from commit 8fac4c4334)

deployment/ceilometer/ceilometer-agent-notification-container-puppet.yaml

@@ -98,17 +98,19 @@ outputs:
         /var/lib/kolla/config_files/ceilometer_agent_notification.json:
           command: /usr/bin/ceilometer-agent-notification --logfile /var/log/ceilometer/agent-notification.log
           config_files:
-            - source: "/var/lib/kolla/config_files/src/*"
-              dest: "/"
-              merge: true
-              preserve_properties: true
-            - if:
-                - ceilometer_enable_panko
-                - source: "/var/lib/kolla/config_files/src-panko/*"
+            list_concat:
+              - - source: "/var/lib/kolla/config_files/src/*"
                   dest: "/"
                   merge: true
                   preserve_properties: true
-                - ''
+              - if:
+                  - ceilometer_enable_panko
+                  - - source: "/var/lib/kolla/config_files/src-panko/*"
+                      dest: "/"
+                      merge: true
+                      preserve_properties: true
+                  - null
+
           permissions:
             - path: /etc/panko
               owner: root:ceilometer