Add default location for cacert_file

Related-Prod: PROD-23403

Change-Id: I1306294c2be355120dd4c02dc52d0b98682beaec
diff --git a/keystone/files/queens/keystone.conf.Debian b/keystone/files/queens/keystone.conf.Debian
index 9b599ea..c4d0c1b 100644
--- a/keystone/files/queens/keystone.conf.Debian
+++ b/keystone/files/queens/keystone.conf.Debian
@@ -1812,6 +1812,7 @@
     {%- set messaging_engine = _data.engine %}
 {%- endif %}
 [oslo_messaging_{{ messaging_engine }}]
+{%- if _data.ssl is defined and 'cacert_file' not in _data.get('ssl', {}).keys() %}{% do _data['ssl'].update({'cacert_file': server.cacert_file}) %}{% endif %}
 {%- include "oslo_templates/files/queens/oslo/messaging/_" + messaging_engine + ".conf" %}
 {%- endif %}