These FDs are closed, so set them to -1 so they are no longer valid.
Signed-off-by: Jason Andryuk <jandryuk@gmail.com> Acked-by: Wei Liu <wl@xen.org> Reviewed-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> Release-acked-by: Paul Durrant <paul@xen.org>