attribute missing in vpn_openvpn_server.php, closes https://github.com/opnsense/core/issues/425

src/www/vpn_openvpn_server.php

@@ -326,7 +326,7 @@ if ($_SERVER['REQUEST_METHOD'] === 'GET') {
             ,serverbridge_dhcp_end,dns_domain,dns_server1,dns_server2,dns_server3
             ,dns_server4,push_register_dns,ntp_server1,ntp_server2,netbios_enable
             ,netbios_ntype,netbios_scope,no_tun_ipv6,verbosity_level,wins_server1
-            ,wins_server2,client_mgmt_port";
+            ,wins_server2,client_mgmt_port,strictusercn";
 
             foreach (explode(",", $copy_fields) as $fieldname) {
                 $fieldname = trim($fieldname);