UnifiedInvokerHAProxy does not implement InvokerProxyHA

UnifiedInvokerHAProxy does not implement InvokerProxyHA. Because of this, ProxyFactoryHA will not update a unified invoker proxy's target list when it gets a notification of a cluster topology change. Effect is a client downloading the proxy will always get the set of targets available when the proxy was created.

Usually the downloaded proxy will also have at least one valid target (the one for the node that created the proxy.) As soon as the client makes an invocation, the server will detect they have a stale view and piggyback the current targets with the response. So, this bug is not very likely to cause an invocation failure, but it does reduce the robustness of the proxy.