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>
```
{
        std::lock_guard lock{mutex};
        if (configs == new_configs)
            return;
        configs = new_configs;
        std::vector<String> removed_names;
        for (auto & [name, info] : infos)
        {
            auto new_config_it = new_configs->find(name);
            if (new_config_it == new_configs->end())
            {
                removed_names.emplace_back(name);
            }
            else
            {
                const auto & new_config = new_config_it->second;