Configure dnsmasq to use dhcp-hosts.conf file

This allows you to put dhcp-host entries in
/etc/lxc/dhcp-hosts.conf and then send SIGHUP to the dnsmasq
process which causes dnsmasq to read the dhcp-hosts.conf file.
This is useful for creating reserved IP's per MAC address.
Ref: --dhcp-host in dnsmasq(8)
Include lxc.hook.clone scripts in default.conf