Don't add to defaults in func init, just add them to cmd

selector/roundrobin/round_robin_selector.go

@@ -3,7 +3,6 @@ package roundrobin
 import (
 	"sync"
 
-	"github.com/micro/go-micro/cmd"
 	"github.com/micro/go-micro/registry"
 	"github.com/micro/go-micro/selector"
 )
@@ -12,10 +11,6 @@ type roundRobinSelector struct {
 	so selector.Options
 }
 
-func init() {
-	cmd.DefaultSelectors["roundrobin"] = NewSelector
-}
-
 func (r *roundRobinSelector) Init(opts ...selector.Option) error {
 	for _, o := range opts {
 		o(&r.so)