Bug fix for create_table where multiple indexes share the same attribute that is not a key attribute.

I'm not sure what's going on with Python 3, but the test needs to be looking at args as opposed to schema as it does in test_global_index, and if you look at the fix in models, you'll agree it's needed. With it, it's possible to create a table with multiple indices that share the same non key attribute. Without it, it's not.