Bluetooth: hci_conn: Fix sending BT_HCI_CMD_LE_CREATE_CONN_CANCEL

This fixes sending BT_HCI_CMD_LE_CREATE_CONN_CANCEL when
hci_le_create_conn_sync has not been called because HCI_CONN_SCANNING
has been clear too early before its cmd_sync callback has been run.

Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>