automatically set nginx-worker based on CPU-count

core/nginx/conf/nginx.conf

@@ -1,6 +1,6 @@
 #  Basic configuration
 user nginx;
-worker_processes 4;
+worker_processes auto;
 error_log /dev/stderr info;
 pid /var/run/nginx.pid;
 load_module "modules/ngx_mail_module.so";