Bluetooth-OPP: Cleanup OPP transfer session after Tx abort

The change will ensure that when user cancelled the tranfer while
ongoing Rx, the transfer session will be cleaned up properly.
Otherwise, while Tx + Rx concurrency if user abort the Tx and
start Tx again new tranfer session will be created only after Rx
is finished.

CRs-Fixed: 585962
Change-Id: I9b5e1c0f1748ccc47811d669ddab96ba43f424f5