Add clients ca_file in heat

This patch fix creating statck resource failure in heat.

Change-Id: I00c23f8b89765e266d045cc463ce4d863d0d6089
Closes-Bug: #1869137

ansible/roles/heat/templates/heat.conf.j2

@@ -89,6 +89,7 @@ policy_file = {{ heat_policy_file }}
 
 [clients]
 endpoint_type = internalURL
+ca_file = {{ openstack_cacert | default(omit) }}
 
 [oslo_middleware]
 enable_proxy_headers_parsing = True

releasenotes/notes/bug-1869137-d3de4debf827e1d2.yaml

+---
+fixes:
+  - |
+    Add client ca_cert file in heat
+    `LP#1869137 <https://bugs.launchpad.net/kolla-ansible/+bug/1869137>`__