feat(`pillar.example`): add stock `log_format`

pillar.example

@@ -135,8 +135,9 @@ nginx:
 
           ### module ngx_http_log_module example
           log_format: |-
-            main '...';
-              access_log /var/log/nginx/access_log main
+            main '$remote_addr - $remote_user [$time_local] $status '
+                                '"$request" $body_bytes_sent "$http_referer" '
+                                '"$http_user_agent" "$http_x_forwarded_for"'
           access_log: []       #suppress default access_log option from being added
 
         ### module nngx_stream_core_module