Code review comment for ~dojordan/cloud-init:azure-preprovisioning

I'd like a response to a comment in my last review:
| without passing in a nic to EphemeralDHCPv4, it will end up calling
| 'find_fallback_nic' each time. I wonder if that behavior is better or
| worse than picking one device and just sticking with it throuh the use
| of this class.

I dont expect that this is a big deal, but a hotplug of a nic during
the wait for the IMDS could result in the interface that is used for
dhcp to be different on retries than on the first.