Merge pull request #67661 from ipuustin/conn-close

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

device manager: don't do operations on nil pointer

**What this PR does / why we need it**:

In the device plugin stub, if `grpc.DialContext()` fails, a `nil` connection is returned. Check the
error before calling `conn.Close()`.

**Release note**:

```release-note
NONE
```

pkg/kubelet/cm/devicemanager/device_plugin_stub.go

@@ -165,10 +165,10 @@ func (m *Stub) Register(kubeletEndpoint, resourceName string, pluginSockDir stri
 		grpc.WithDialer(func(addr string, timeout time.Duration) (net.Conn, error) {
 			return net.DialTimeout("unix", addr, timeout)
 		}))
-	defer conn.Close()
 	if err != nil {
 		return err
 	}
+	defer conn.Close()
 	client := pluginapi.NewRegistrationClient(conn)
 	reqt := &pluginapi.RegisterRequest{
 		Version:      pluginapi.Version,