vhost-user-test: use unix port for migration TCP port 1234 may be used by another process concurrently. Instead use a temporary unix socket. Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>