SD.eureka: register app to instance ignore status

when registrar get instances from eureka server app, it ignore eureka app status.

```go
func convertFargoAppToInstances(app *fargo.Application) []string {
instances := make([]string, len(app.Instances))
for i, inst := range app.Instances {
instances[i] = fmt.Sprintf("%s:%d", inst.IPAddr, inst.Port)
}
return instances
}
```

How can i filter them? (eg: I only want STATUS = 'UP' instance)
```go
func convertFargoAppToInstances(app *fargo.Application) []string {
var instances []string
for _, inst := range app.Instances {
if inst.Status == fargo.UP {
instances = append(instances, fmt.Sprintf("%s:%d", inst.IPAddr, inst.Port))
}
}
return instances
}
```