master ui add raft stats and Max Volume Id

weed/server/master_server_handlers_ui.go

@@ -15,6 +15,7 @@ import (
 func (ms *MasterServer) uiStatusHandler(w http.ResponseWriter, r *http.Request) {
 	infos := make(map[string]interface{})
 	infos["Up Time"] = time.Now().Sub(startTime).String()
+	infos["Max Volume Id"] = ms.Topo.GetMaxVolumeId()
 	if ms.Topo.RaftServer != nil {
 		args := struct {
 			Version           string