move DiskStatus and MemStatus to protobuf

weed/stats/disk_notsupported.go

@@ -2,6 +2,8 @@
 
 package stats
 
-func (disk *DiskStatus) fillInStatus() {
+import "github.com/chrislusf/seaweedfs/weed/pb/volume_server_pb"
+
+func fillInDiskStatus(status *volume_server_pb.DiskStatus) {
 	return
 }