Bluetooth: hci_sync: Cleanup hci_conn if it cannot be aborted

This attempts to cleanup the hci_conn if it cannot be aborted as
otherwise it would likely result in having the controller and host
stack out of sync with respect to connection handle.

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>