dnsmasq.conf: fixed DB module name. Refs #2916

esmith::InterfacesDB obsoleted by esmith::NetworksDB.
dnsmasq.conf: removd tftp-secure option. Refs #2916

The tftp-secure option restrict TFTP access to files owned by the user
running dnsmasq (nobody here). This conflicts with the convention that
states "nobody" can't own any file or directory on the system.

Moreover FS access is formerly limited to /var/lib/tftproot by
tftp-root option.