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>
```
if (auto it = infos.find(name); it != infos.end())
            {
                const auto & info = it->second;
                if (info.loaded() || info.isLoading())
                    LOG_TRACE(log, "Unloading '{}' because its configuration has been removed or detached", name);
                infos.erase(it);
            }
        }
        
        
        
        event.notify_all();
    }
    
    void enableAlwaysLoadEverything(bool enable)
    {
        std::lock_guard lock{mutex};
        if (always_load_everything == enable)
            return;
        always_load_everything = enable;
        if (enable)
        {
            
            for (auto & [name, info] : infos)
                if (!info.triedToLoad())
                    startLoading(info);
        }
    }
    
    void enableAsyncLoading(bool enable)