MDNS registry fix for users on VPNs (#1759)

* filter out unsolicited responses
* send to local ip in case
* allow ip func to be passed in. add option for sending to 0.0.0.0

registry/mdns_registry.go

@@ -252,7 +252,7 @@ func (m *mdnsRegistry) Register(service *Service, opts ...RegisterOption) error
 			continue
 		}
 
-		srv, err := mdns.NewServer(&mdns.Config{Zone: s})
+		srv, err := mdns.NewServer(&mdns.Config{Zone: s, LocalhostChecking: true})
 		if err != nil {
 			gerr = err
 			continue