**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)
Handshake handshake(server_capability_flags, connection_id, VERSION_STRING + String("-") + VERSION_NAME,
            auth_plugin->getName(), auth_plugin->getAuthPluginData(), CharacterSet::utf8_general_ci);
        packet_endpoint->sendPacket<Handshake>(handshake, true);
        LOG_TRACE(log, "Sent handshake");
        HandshakeResponse handshake_response;
        finishHandshake(handshake_response);
        connection_context.mysql.client_capabilities = handshake_response.capability_flags;
        if (handshake_response.max_packet_size)
            connection_context.mysql.max_packet_size = handshake_response.max_packet_size;
        if (!connection_context.mysql.max_packet_size)
            connection_context.mysql.max_packet_size = MAX_PACKET_LENGTH;
        LOG_TRACE(log,
            "Capabilities: {}, max_packet_size: {}, character_set: {}, user: {}, auth_response length: {}, database: {}, auth_plugin_name: {}",
            handshake_response.capability_flags,
            handshake_response.max_packet_size,
            static_cast<int>(handshake_response.character_set),
            handshake_response.username,
            handshake_response.auth_response.length(),
            handshake_response.database,
            handshake_response.auth_plugin_name);
        client_capability_flags = handshake_response.capability_flags;
        if (!(client_capability_flags & CLIENT_PROTOCOL_41))
            throw Exception("Required capability: CLIENT_PROTOCOL_41.", ErrorCodes::MYSQL_CLIENT_INSUFFICIENT_CAPABILITIES);
        authenticate(handshake_response.username, handshake_response.auth_plugin_name, handshake_response.auth_response);
        try
        {
            if (!handshake_response.database.empty())
                connection_context.setCurrentDatabase(handshake_response.database);
            connection_context.setCurrentQueryId(Poco::format("mysql:%lu", connection_id));
        }