Description:
------------
With PDO, when dropping a table, the driver emits a `ROLLBACK`, and so close the transaction. It should not.

I tested it with a raw CLI connection, and it works well.

MySQL Logs
```
210412 10:17:07     77 Connect  root@172.21.0.2 as anonymous on rio
                    77 Query    START TRANSACTION
                    77 Query    CREATE TEMPORARY TABLE greg
(
    source_input LONGTEXT DEFAULT NULL COLLATE `utf8mb4_bin`,
    INDEX source_input_index (source_input (12) )
)
                    77 Query    DELETE FROM greg
                    77 Query    DROP TABLE greg
                    77 Query    ROLLBACK
                    77 Quit
```

Note: The following code work well on PHP 7.4

Note2: To enable MySQL Logs at runtime:
```
SET GLOBAL general_log = 'ON';
SET GLOBAL general_log_file = '/var/log/mysql/mysql.log';
```

Test script:
---------------
$conn = new PDO('mysql:dbname=rio;host=database', 'root', 'rio');
$conn->beginTransaction();
$conn->exec(<<<'EOSQL'
CREATE TEMPORARY TABLE greg
(
    source_input LONGTEXT DEFAULT NULL COLLATE `utf8mb4_bin`,
    INDEX source_input_index (source_input (12) )
)
EOSQL);
var_dump($conn->inTransaction()); // true
$conn->exec('DELETE FROM greg');
var_dump($conn->inTransaction()); // true
$conn->exec('DROP TABLE greg');
var_dump($conn->inTransaction()); // false, but it should not
$conn->commit(); // Throw an exception because there is not transaction

Expected result:
----------------
bool(true)
bool(true)
bool(true)


Actual result:
--------------
bool(true)
bool(true)
bool(false)
PDOException {#844
  #message: "There is no active transaction"
  #code: 0
  #file: "./test.php"
  #line: 44
  +errorInfo: null
  trace: {
    ./test.php:44 {
      › var_dump($conn->inTransaction());
      › $conn->commit();
      › 
    }
  }
}