**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)
{
    String database;
    readStringUntilEOF(database, payload);
    LOG_DEBUG(log, "Setting current database to {}", database);
    connection_context.setCurrentDatabase(database);
    packet_endpoint->sendPacket(OKPacket(0, client_capability_flags, 0, 0, 1), true);
}
void MySQLHandler::comFieldList(ReadBuffer & payload)
{
    ComFieldList packet;
    packet.readPayloadWithUnpacked(payload);
    String database = connection_context.getCurrentDatabase();
    StoragePtr table_ptr = DatabaseCatalog::instance().getTable({database, packet.table}, connection_context);
    auto metadata_snapshot = table_ptr->getInMemoryMetadataPtr();
    for (const NameAndTypePair & column : metadata_snapshot->getColumns().getAll())
    {
        ColumnDefinition column_definition(
            database, packet.table, packet.table, column.name, column.name, CharacterSet::binary, 100, ColumnType::MYSQL_TYPE_STRING, 0, 0
        );
        packet_endpoint->sendPacket(column_definition);
    }
    packet_endpoint->sendPacket(OKPacket(0xfe, client_capability_flags, 0, 0, 0), true);
}
void MySQLHandler::comPing()