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::unique_lock lock{mutex};
        loadImpl(filter, timeout, true, lock);
        return collectLoadResults<ReturnType>(filter);
    }
    bool has(const String & name) const
    {
        std::lock_guard lock{mutex};
        return infos.contains(name);
    }
    
    
    void reloadOutdated()
    {
        
        std::unordered_map<LoadablePtr, bool> should_update_map;
        {
            std::lock_guard lock{mutex};
            TimePoint now = std::chrono::system_clock::now();
            for (const auto & name_and_info : infos)
            {
                const auto & info = name_and_info.second;
                if ((now >= info.next_update_time) && !info.isLoading() && info.loaded())
                    should_update_map.emplace(info.object, info.failedToReload());