Add MasqueradeAddress support to FTP Flexshares
Migrated from: https://tracker.clearos.com/view.php?id=216
Reported by: Peter Baldwin
The MasqueradeAddress parameter is very useful for systems running a public FTP server behind a NAT-based firewall.
References - http://www.proftpd.org/docs/directives/linked/config_ref_MasqueradeAddress.html