change server address from string to a type

weed/shell/command_volume_delete.go

@@ -2,6 +2,7 @@ package shell
 
 import (
 	"flag"
+	"github.com/chrislusf/seaweedfs/weed/pb"
 	"io"
 
 	"github.com/chrislusf/seaweedfs/weed/storage/needle"
@@ -41,7 +42,7 @@ func (c *commandVolumeDelete) Do(args []string, commandEnv *CommandEnv, writer i
 		return nil
 	}
 
-	sourceVolumeServer := *nodeStr
+	sourceVolumeServer := pb.ServerAddress(*nodeStr)
 
 	volumeId := needle.VolumeId(*volumeIdInt)