Code review comment for ~smoser/curtin:cleanup/always-use-bootif

Ryan,
good catch on hostname.
you were right, I documented the *wrong* format.
Apparently googles' answer to 'klibc ipconfig' was wrong:
  https://kernel.googlesource.com/pub/scm/libs/klibc/klibc/+/klibc-0.130/ipconfig/README
There it is documented:
  addr:server:gateway:netmask:interface:proto

But Ubuntu's version:
  https://git.launchpad.net/ubuntu/+source/klibc/tree/usr/kinit/ipconfig/README.ipconfig
documents (and uses):
  <client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>

So my code was right, but doc was wrong. They're fixed now.