remove data race on the devicemanager client plugin

Change-Id: I45b85440a792e5ed2f75a344ec1f0332854d8d6d

pkg/kubelet/cm/devicemanager/plugin/v1beta1/client.go

@@ -69,8 +69,10 @@ func (c *client) Connect() error {
 		klog.ErrorS(err, "Unable to connect to device plugin client with socket path", "path", c.socket)
 		return err
 	}
+	c.mutex.Lock()
 	c.grpc = conn
 	c.client = client
+	c.mutex.Unlock()
 	return c.handler.PluginConnected(c.resource, c)
 }