Have the VMs get their IPs via DHCP/metdata

Currently, VMs are hard-assigned their IPs via the zephyr API call. However, it would be useful to test the DHCP and metadata features of the network system by having the VMs make DHCP calls to 169.254.169.254 instead.

This is simply a matter of making dhclient calls in the VM's namespace upon boot in the create_cm call (for each of the underlay system classes), where zephyr normally assigns the interface and sets the IP.