Disable seccomp sandboxing in vsftpd

This fix the ANSTE tests and allow to write without giving the annoying problem of 500 OOPS: priv_sock_get_cmd

https://bugs.launchpad.net/ubuntu/+source/vsftpd/+bug/1195816

http://technologytales.com/2013/09/21/turning-off-seccomp-sandbox-in-vsftpd/