CD/DVD drive with installation ISO should be exactly the 2nd device in the VM boot order.
This ensures that VM will boot from this ISO at the first boot time only.
For each ISO image the individual cdrom device will be added to the VM. During the cleanup these devices will be deleted.
It makes attach steps more clear - there is no doubt what is the name of the device.
Related to: [mitchellh/packer#1502]
Remove the redundant StepRemoveDevices and rely on the cleanup to be handled by:
* StepAttachParallelsTools.Cleanup
* StepAttachFloppy.Cleanup
* stepAttachISO.Cleanup
"guest_os_distribution" become deprecated and is not required anymore.
But if it is defined (in outdated templates),then the value will be copied to "guest_os_type" and warning will be displayed.
The IP address that the guest OS connect to download files from the
http_dir is determined by searching for a host interface with an IP
assigned. Now it is possible to use host_interfaces to select which
interfaces are searched.