packaging: setup: boot from disk on additional hosts

On additional hosts the VM will always boot from disk
because there is no reason for providing an install
media since the VM has been already installed on
first host.
Set to None also ovf and cdrom iso path: they were
paths valid on first host, not on additonal hosts.

Change-Id: Iba6ee40c08379ca3713fef3b5e7f10a190268880
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>