image-serve: improve vhost config

- Add logging options
- Disable ServerSignature
- Allow X-Forwarded-Proto for https

Change-Id: I206e1417702b47b2e1dab3ec7ae211b5a2501f61

roles/tripleo-image-serve/templates/image-serve.conf.j2

@@ -1,6 +1,10 @@
 Listen {{ container_registry_port }}
 <VirtualHost {{ container_registry_host }}:{{ container_registry_port }}>
     DocumentRoot {{ image_data_dir }}
+    ErrorLog "/var/log/httpd/image_serve_error.log"
+    ServerSignature Off
+    CustomLog "/var/log/httpd/image_serve_access.log" combined
+    SetEnvIf X-Forwarded-Proto https HTTPS=1
 
     <Directory {{ image_data_dir }}>
         # This assumes a file exists containing {} at