Fixing harsh upgrade_proto for `"BatchNorm"` layer

src/caffe/util/upgrade_proto.cpp

@@ -1018,7 +1018,13 @@ void UpgradeNetBatchNorm(NetParameter* net_param) {
     // the previous BatchNorm layer definition.
     if (net_param->layer(i).type() == "BatchNorm"
         && net_param->layer(i).param_size() == 3) {
-      net_param->mutable_layer(i)->clear_param();
+      // set lr_mult and decay_mult to zero. leave all other param intact.
+      for (int ip = 0; ip < net_param->layer(i).param_size(); ip++) {
+        ParamSpec* fixed_param_spec =
+          net_param->mutable_layer(i)->mutable_param(ip);
+        fixed_param_spec->set_lr_mult(0.f);
+        fixed_param_spec->set_decay_mult(0.f);
+      }
     }
   }
 }