qmp-event: add event notification for memory hot unplug error When memory hot unplug fails, this patch adds support to send QMP event to notify mgmt about this failure. Reviewed-by: Igor Mammedov <imammedo@redhat.com> Signed-off-by: Zhu Guihua <zhugh.fnst@cn.fujitsu.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>