Fix is_rx for receive_own_messages for Kvaser

[btRooke]

Context and changes

Most other interfaces set is_rx to False if a transmitted message is received when receive_own_messages is enabled.

This previously wasn't the case for Kvaser.

Enabling the LOCAL_TXACK flag allows us to determine this.

Testing

This can be manually tested with a simple script:

import can
import time

msg = can.Message(
    arbitration_id=0xC0FFEE, data=[0, 25, 0, 1, 3, 1, 4, 1],
    is_extended_id=True
)

with can.Bus(receive_own_messages=True) as bus:
    notifier = can.Notifier(bus, [can.Printer()])
    bus.send_periodic(msg, 0.5)
    time.sleep(3)

Before this change, transmitted messages will be printed as "Rx", after as "Tx".

Do let me know if there's some obvious way to check this in automated tests.