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>
```
bool check_no_errors) const
{
    std::exception_ptr exception;
    for (const auto & result : results)
    {
        try
        {
            checkLoaded(result, check_no_errors);
        }
        catch (...)
        {
            if (!exception)
                exception = std::current_exception();
            else
                tryLogCurrentException(log);
        }
    }
    if (exception)
        std::rethrow_exception(exception);
}
void ExternalLoader::reloadConfig() const
{
    loading_dispatcher->setConfiguration(config_files_reader->read());
}
void ExternalLoader::reloadConfig(const String & repository_name) const
{
    loading_dispatcher->setConfiguration(config_files_reader->read(repository_name));
}
void ExternalLoader::reloadConfig(const String & repository_name, const String & path) const