Hello,

so I'm working to integrate CatBoost model with our ClickHouse cluster. It appears that, whenever we create a new XML model file in the configured path, the **first** call to the new model never returns (this is true both of the HTTP interface as well as via clickhouse-client).

Independently from whether the locked statement gets cancelled, subsequent calls succeed immediately.

```
16e8bdb5bbb9 :) select version();

SELECT version()

┌─version()─┐
│ 20.6.3.28 │
└───────────┘

1 rows in set. Elapsed: 0.006 sec.
```

Is this known behavior? If it helps, my models look like this:

```
<models>
    <model>
        <type>catboost</type>
        <name>ctr_predictor</name>
        <path>/catboost/my_predictor</path>
        <lifetime>0</lifetime>
    </model>
</models>
```
{
    config_files_reader->setConfigSettings(settings);
}
void ExternalLoader::enableAlwaysLoadEverything(bool enable)
{
    loading_dispatcher->enableAlwaysLoadEverything(enable);
}
void ExternalLoader::enableAsyncLoading(bool enable)
{
    loading_dispatcher->enableAsyncLoading(enable);
}
void ExternalLoader::enablePeriodicUpdates(bool enable_)
{
    periodic_updater->enable(enable_);
}
bool ExternalLoader::hasLoadedObjects() const
{
    return loading_dispatcher->hasLoadedObjects();
}
ExternalLoader::Status ExternalLoader::getCurrentStatus(const String & name) const
{
    return loading_dispatcher->getCurrentStatus(name);
}
template <typename ReturnType, typename>
ReturnType ExternalLoader::getLoadResult(const String & name) const
{
    return loading_dispatcher->getLoadResult<ReturnType>(name);
}
template <typename ReturnType, typename>
ReturnType ExternalLoader::getLoadResults(const FilterByNameFunction & filter) const