roles/nginx: Don't cache 404 errors in munin config

Signed-off-by: Alan Orth <alan.orth@gmail.com>

roles/nginx/files/munin.conf

@@ -2,6 +2,8 @@
 server {
     listen localhost:80;
 
+    log_not_found off;
+
     location /nginx_status {
         stub_status on;
         access_log off;