This allows to interate over an event group.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20210601132414.432430-4-kraxel@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>