OSU-Net/cyder — pull request #397 by drkitty (2013-10-10 20:20:31+00:00)
Title: DHCP class generation fixes

```irc
12:38 Each VRF generates a class, which has a subclass for each dynamic interface in the VRF. Did you say we should also build subclasses for the static interfaces in the VRF?
...
12:38 every mac in the vrf
```

This pull request changes `Vrf.build_vrf` to match that behavior, as well as improving the general efficiency of DHCP class generation.