DHCP is provided by *dns1.pyrocufflink.blue* now, not the gateway. To
allow dynamic DNS updates from it, the correct source address must be
listed in the zone configuration for *pyrocufflink.red*.
In order to support adding a second DNS server, the BIND zone
configuration needs to be partially modularized. While the forwarder
definitions for *pyrocufflink.blue*, etc. will remain the same, the
*pyrocufflink.red* zone will be different, as it will be a slave zone on
the second server. This commit breaks up the definition of the
`named_zones` variable into two parts:
* `pyrocufflink_red_zones`: This is a list of zone objects for
*pyrocufflink.red* and its corresponding reverse zone. On
*dns1.pyrocufflink.blue*, these are master zones. On the new server,
these will be slaves.
* `pyrocufflink_common_zones`: This is a list of zone objects for the
zones that are the same on both servers, since they are all forwarding
zones.
Similarly, the `named_keys` variable only needs to be defined on the
master, since DHCP will only send updates there.
Dustin