only include PostgreSQL role when deploying an internal database

Author: evgeni

src/playbooks/deploy/deploy.yaml

@@ -57,7 +57,9 @@
         certificate_checks_certificate: "{{ server_certificate }}"
         certificate_checks_key: "{{ server_key }}"
         certificate_checks_ca: "{{ ca_certificate }}"
-    - postgresql
+    - role: postgresql
+      when:
+        - database_mode == 'internal'
     - redis
     - candlepin
     - httpd