https://bugzilla.redhat.com/show_bug.cgi?id=808463

Well, libvirt doesn't distinguish between domain poweroff and
hibernation (S4). It's hard to differentiate these two on a real
machine anyway. As a result, any device that is hot(un-)plugged is
lost (appears again) when domain is started again as from our POV
it is a fresh cold boot. Instead of doing anything wise here, we
should just document this as known limitation.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>