Valid config that omits the 'name' field is rejected

[tjohnes]

Per the multi-network CRD spec, if spec.config is valid but omits the name field, then the NPWG implementation adds a name field containing the NAD name (section 3.4.2).

preprocessCNIConfig attempts to mirror this behavior, but it only adds the name if there is an error unmarshalling the config:

	if err := json.Unmarshal(config, &c); err != nil {
		if n, ok := c["name"]; !ok || n == "" {
			c["name"] = name
		}
	}

This means valid config that omits the name field is rejected by the webhook.