Dhcpd: support a wider variety of DHCP allow/deny/ignore statement

The Dhcpd.aug was missing a part of the allow/deny/ignore possible
statement. This commit updates the lense so it supports the list
of options available here

http://www.ipamworldwide.com/declarations-topological/declarations-allowdenyignore.html

Also this bug was preventing a Foreman user to parse the dhcpd.conf
generated by theforeman/dhcp puppet module