Override the configuration upon boot

We were previously appending to the file, so we ended up with
repeated declarations - which made nginx error

Author: matiasgarciaisaia

files/runit-nginx-run

@@ -2,7 +2,7 @@
 
 if [ -n "$NGINX_RAILS__client_max_body_size" ]
 then
-  echo "client_max_body_size $NGINX_RAILS__client_max_body_size;" >> /etc/nginx/conf.d/nginx_rails_runtime.conf
+  echo "client_max_body_size $NGINX_RAILS__client_max_body_size;" > /etc/nginx/conf.d/nginx_rails_runtime.conf
 fi
 
 /usr/sbin/nginx -g 'daemon off;'