Bluetooth: Use the correct flag to decide to disable advertising

When deciding to call disable_advertising() we're interested in the real
state instead of the mgmt setting. Use therefore HCI_LE_ADV instead of
the HCI_ADVERTISING flag.

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>