Bluetooth: Fix trying to disable scanning twice

The discovery process has a timer for disabling scanning, however
scanning might be disabled through other means too like the auto-connect
process.  We should therefore ensure that the timer is never active
after sending a HCI command to disable scanning.

There was some existing code in stop_scan_complete trying to avoid the
timer when a connect request interrupts a discovery procedure, but the
other way around was not covered. This patch covers both scenarios by
canceling the timer as soon as we get a successful command complete for
the disabling HCI command.
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/hci_conn.c

@@ -628,7 +628,6 @@ static void stop_scan_complete(struct hci_dev *hdev, u8 status)
 	/* Since we may have prematurely stopped discovery procedure, we should
 	 * update discovery state.
 	 */
-	cancel_delayed_work(&hdev->le_scan_disable);
 	hci_discovery_set_state(hdev, DISCOVERY_STOPPED);
 
 	hci_req_init(&req, hdev);

net/bluetooth/hci_event.c

@@ -1018,6 +1018,11 @@ static void hci_cc_le_set_scan_enable(struct hci_dev *hdev,
 		break;
 
 	case LE_SCAN_DISABLE:
+		/* Cancel this timer so that we don't try to disable scanning
+		 * when it's already disabled.
+		 */
+		cancel_delayed_work(&hdev->le_scan_disable);
+
 		clear_bit(HCI_LE_SCAN, &hdev->dev_flags);
 		break;