reduce duplicated code by using a tree of Node

weed-fs/src/pkg/topology/server.go

@@ -0,0 +1,21 @@
+package topology
+
+import (
+  "pkg/storage"
+)
+
+type Server struct {
+  Node
+	volumes     map[storage.VolumeId]*storage.VolumeInfo
+	Ip          NodeId
+	Port        int
+	PublicUrl   string
+}
+func (s *Server) CreateOneVolume(r int, vid storage.VolumeId) storage.VolumeId {
+  s.AddVolume(&storage.VolumeInfo{Id:vid, Size: 32*1024*1024*1024})
+  return vid
+}
+func (s *Server) AddVolume(v *storage.VolumeInfo){
+  s.volumes[v.Id] = v
+  s.Node.AddVolume(v)
+}