fix review comment

config_center/configuration_listener.go

registry/base_configuration_listener.go

registry/consul/listener.go

registry/consul/registry.go

registry/etcdv3/listener.go

registry/event.go

registry/event_listener.go

registry/kubernetes/listener.go

registry/mock_registry.go

registry/nacos/listener.go

registry/nacos/registry.go

registry/protocol/protocol.go

registry/zookeeper/registry.go