Storage attr fix

[mdrichardson]

Fixes instances where item.get("e_tag") fails due to item not being a dict, but having the "e_tag" attribute. Also changed a few instances where this was working fine to match the new "style" of this fix:

e_tag = None
if isinstance(item, dict):
  e_tag = item.get("e_tag", None)
elif hasattr(item, "e_tag"):
  e_tag = item.e_tag

All current tests pass (with EMULATOR_RUNNING = True, of course)