**Describe the bug**
ClickHouse doesn't return affected rows via MySQL protocol for INSERT queries after 20.5+

**How to reproduce**
i create clear docker-compose environment for reproduce behavior MySQL + clickhouse + php + python
https://gist.github.com/Slach/aa67440ce856a3a53f64f92eeddfbc1b

**Queries to run that lead to unexpected result**
```
INSERT INTO default.t1(n) SELECT * FROM numbers(1000)
```

**Expected behavior**
MySQL protocol shall return affected rows field for INSERT queries (it works successful in 20.3 and 20.4)
![image](https://user-images.githubusercontent.com/105560/97867431-aa22ae00-1d2f-11eb-8caf-05431ffd29b3.png)

**Actual behavior**
![image](https://user-images.githubusercontent.com/105560/97867401-9f681900-1d2f-11eb-93cc-5ae6f1f5981b.png)
" metadata_modification_time AS Create_time,"
            " metadata_modification_time AS Update_time,"
            " metadata_modification_time AS Check_time,"
            " 'utf8_bin' AS Collation,"
            " 'NULL' AS Checksum,"
            " '' AS Create_options,"
            " '' AS Comment"
            " FROM system.tables"
            " WHERE name LIKE "
            + suffix);
    }
    return query;
}
static String killConnectionIdReplacementQuery(const String & query)
{
    const String prefix = "KILL QUERY ";
    if (query.size() > prefix.size())
    {
        String suffix = query.data() + prefix.length();
        static const std::regex expr{"^[0-9]"};
        if (std::regex_match(suffix, expr))
        {
            String replacement = Poco::format("KILL QUERY WHERE query_id = 'mysql:%s'", suffix);
            return replacement;
        }
    }
    return query;
}
}