Device unplug can be done asynchronously. Thus, sending the second
device_del before the previous unplug is complete may lead to
unexpected results. On PCIe devices, this cancels the hot-unplug
process.

Signed-off-by: Julia Suvorova <jusual@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20200220165556.39388-1-jusual@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>