Install improvements

Hi Lucas, this series is about running the unattended_install tests from the test runner.  So there are some improvements to unattended_install.py and some to the guest-os files.  I found out that ks=floppy doesn't work in newer Fedoras and I've dropped that. I also fixed unattended_install.url, which was still expecting a CD-ROM for the installation repository.

For now I'm still using a separate config file, but I managed to use one that is quite simple:

    include qemu/cfg/tests-shared.cfg
    
    qemu_binary = /usr/bin/qemu-kvm
    qemu_img_binary = /usr/bin/qemu-img
    qemu_io_binary = /usr/bin/qemu-io
    only qcow2
    only virtio_net
    only virtio_blk
    only smp2
    only no_9p_export
    only no_pci_assignable
    only smallpages
    only JeOS
    only i440fx
    
    only unattended_install.url
    only extra_cdrom_ks

And perhaps it's not even needed anymore, just that a) I haven't tried; b) I wanted to understand how -c works. :)

It's a bit late, and my install hasn't finished yet, but it's an improvement anyway. I can follow-up tomorrow.