If your using configuration drive, cloud init tries to DHCP by
default anyway, which delays the boot sequence as it seeks out a
network attached metadata source.
So instead, disable the automatic activation so the configuration
drive data source is acutally leverage. Additionally add further
notes to provide guidance to users of DIB.
Change-Id: Ie7c522f23deb3f08ee4ec002e0e2020f382359aa