Valgrind complains that virtio_user is calling close(-1).
Fix this by adding check in virtio that is similar to existing code.
Fixes: 37a7eb2ae816 ("net/virtio-user: add device emulation layer")
Cc: stable@dpdk.org
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Reviewed-by: Tiwei Bie <tiwei.bie@intel.com>