add table_name to fix "order created_at" excpetion error

* fix for Issue #3305
* include a test

```bash
localhost:core xwaynec$ bundle exec rspec spec/models/spree/order_spec.rb
Instance method "open" is already defined in Object, use generic helper instead or set StateMachine::Machine.ignore_method_conflicts = true.
......................................DEPRECATION WARNING: [SPREE] Spree::Order#remove_variant will be deprecated in Spree 2.1, please use order.contents.remove instead. (called from remove_variant at /Users/xwaynec/Project/spree/core/app/models/spree/order.rb:275)
.DEPRECATION WARNING: [SPREE] Spree::Order#remove_variant will be deprecated in Spree 2.1, please use order.contents.remove instead. (called from remove_variant at /Users/xwaynec/Project/spree/core/app/models/spree/order.rb:275)
.DEPRECATION WARNING: [SPREE] Spree::Order#remove_variant will be deprecated in Spree 2.1, please use order.contents.remove instead. (called from remove_variant at /Users/xwaynec/Project/spree/core/app/models/spree/order.rb:275)
.....................

Finished in 3.58 seconds
61 examples, 0 failures
```