delete unused function

weed/util/config.go

@@ -1,8 +1,6 @@
 package util
 
 import (
-	"fmt"
-
 	"github.com/chrislusf/seaweedfs/weed/glog"
 	"github.com/spf13/viper"
 )
@@ -48,13 +46,3 @@ func Config() Configuration {
 	return viper.GetViper()
 }
 
-func SubConfig(subKey string) (Configuration, error) {
-	if subKey != "" {
-		sub := viper.GetViper().Sub(subKey)
-		if sub == nil {
-			return nil, fmt.Errorf("sub config [%s] not exist", subKey)
-		}
-		return sub, nil
-	}
-	return  viper.GetViper(), nil
-}