fix: turn off error logging for validate config

This will allow validation to work if the default logging locations cannot be written to but the configuration is otherwise okay. This will be the case for users with custom nginx configurations that log to other places, such as syslog.

plugins/nginx-vhosts/templates/validate.conf.sigil

@@ -1,2 +1,6 @@
 events { worker_connections 768; }
-http { include {{ $.NGINX_CONF }}; }
+http {
+  access_log off;
+  error_log /dev/null;
+  include {{ $.NGINX_CONF }};
+}