https://bugzilla.redhat.com/show_bug.cgi?id=1462060

When building a qemu namespace we might be dealing with bare
regular files. Files that live under /dev. For instance
/dev/my_awesome_disk:

  <disk type='file' device='disk'>
    <driver name='qemu' type='qcow2'/>
    <source file='/dev/my_awesome_disk'/>
    <target dev='vdc' bus='virtio'/>
  </disk>

  # qemu-img create -f qcow2 /dev/my_awesome_disk 10M

So far we were mknod()-ing them which is
obviously wrong. We need to touch the file and bind mount it to
the original:

1) touch /var/run/libvirt/qemu/fedora.dev/my_awesome_disk
2) mount --bind /dev/my_awesome_disk /var/run/libvirt/qemu/fedora.dev/my_awesome_disk

Later, when the new /dev is built and replaces original /dev the
file is going to live at expected location.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>