noccp pppd option added.

Thanks to Gordon Messmer https://bugzilla.redhat.com/show_bug.cgi?id=887674#c26

src/nm-l2tp-service.c

@@ -1246,6 +1246,10 @@ nm_l2tp_config_write (NML2tpPlugin *plugin,
 	/* Don't need to auth the L2TP server */
 	write_config_option (pppopt_fd, "noauth\n");
 
+	/* pppd and xl2tpd on Linux require this option to support Android and iOS clients,
+	   and pppd on Linux clients won't work without the same option */
+	write_config_option (pppopt_fd, "noccp\n");
+
 	if (service_priv && strlen (service_priv->username)) {
 		write_config_option (pppopt_fd, "name %s\n", service_priv->username);
 	}