turn on streaming assign file id

weed/server/filer_server_handlers_write.go

@@ -43,7 +43,7 @@ func (fs *FilerServer) assignNewFileInfo(so *operation.StorageOption) (fileId, u
 
 	ar, altRequest := so.ToAssignRequests(1)
 
-	assignResult, ae := operation.Assign(fs.filer.GetMaster, fs.grpcDialOption, ar, altRequest)
+	assignResult, ae := fs.assignProxy.Assign(ar, altRequest)
 	if ae != nil {
 		glog.Errorf("failing to assign a file id: %v", ae)
 		err = ae