better no ui setup - install from image - support no MAC addr

Adds more parameters for completely unattended setup, even when
using a pre-configured disk image (rather than an iso).  If the
given disk image exists, use it instead of installing from iso.
This means if it already exists, but you want to install from
scratch, you must delete the disk image first.  Allow installation
if there is no pre-configured MAC addr, IP addr, and hostname, and
grab the IP address from the vm.  Use qcow2 as the default format.