heatwave_utils.list_secondary_engine_tables() fails with classic protocol

```
JS  heatwave_utils.list_secondary_engine_tables('airline')
heatwave_utils.list_secondary_engine_tables: User-defined function threw an exception: 
Traceback (most recent call last):
  File "init.py", line 158, in list_sec_engine_tables
AttributeError: unknown attribute: get_schema
 (ScriptingError)
```