Update go-cni to 40bcf8ec8acd7372be1d77031d585d5d8e561c90.

Signed-off-by: Lantao Liu <lantaol@google.com>

vendor.conf

@@ -6,7 +6,7 @@ github.com/containerd/console c12b1e7919c14469339a5d38f2f8ed9b64a9de23
 github.com/containerd/containerd 15f19d7a67fa322e6de0ef4c6a1bf9da0f056554
 github.com/containerd/continuity bd77b46c8352f74eb12c85bdc01f4b90f69d66b4
 github.com/containerd/fifo 3d5202aec260678c48179c56f40e6f38a095738c
-github.com/containerd/go-cni 6d7b509a054a3cb1c35ed1865d4fde2f0cb547cd
+github.com/containerd/go-cni 40bcf8ec8acd7372be1d77031d585d5d8e561c90
 github.com/containerd/go-runc 5a6d9f37cfa36b15efba46dc7ea349fa9b7143c3
 github.com/containerd/ttrpc 2a805f71863501300ae1976d29f0454ae003e85a
 github.com/containerd/typeurl a93fcdb778cd272c6e9b3028b2f42d813e785d40

vendor/github.com/containerd/go-cni/cni.go

@@ -18,6 +18,7 @@ package cni
 
 import (
 	"fmt"
+	"strings"
 	"sync"
 
 	cnilibrary "github.com/containernetworking/cni/libcni"
@@ -127,6 +128,15 @@ func (c *libcni) Remove(id string, path string, opts ...NamespaceOpts) error {
 	}
 	for _, network := range c.networks {
 		if err := network.Remove(ns); err != nil {
+			// Based on CNI spec v0.7.0, empty network namespace is allowed to
+			// do best effort cleanup. However, it is not handled consistently
+			// right now:
+			// https://github.com/containernetworking/plugins/issues/210
+			// TODO(random-liu): Remove the error handling when the issue is
+			// fixed and the CNI spec v0.6.0 support is deprecated.
+			if path == "" && strings.Contains(err.Error(), "no such file or directory") {
+				continue
+			}
 			return err
 		}
 	}