Add ceilometer user to panko group

Panko is a library for Ceilometer and Ceilometer needs rights
for reading Panko's configuration after rights was restricted to
Panko group.

Change-Id: Ied4e7966c47a4daa69e128b0a08b5864c230014e
Related-Prod: https://mirantis.jira.com/browse/PROD-23782
diff --git a/ceilometer/server/backend/gnocchi.yml b/ceilometer/server/backend/gnocchi.yml
index 723d58c..6ebf45f 100644
--- a/ceilometer/server/backend/gnocchi.yml
+++ b/ceilometer/server/backend/gnocchi.yml
@@ -22,3 +22,19 @@
           enabled: true
           url: "notifier://?topic=${_param:openstack_event_alarm_topic}"
           publish_event: true
+  # default permissions in panko configuration files and ssl certificates are restricted
+  # to panko group, therefore ceilometer must have those permission to have ability to
+  # connect to panko's backend db
+  linux:
+    system:
+      group:
+        panko:
+          enabled: true
+      user:
+        ceilometer:
+          enabled: true
+          name: 'ceilometer'
+          home: '/var/lib/ceilometer'
+          shell: '/bin/false'
+          groups:
+            - 'panko'