Add default ReturnAuthorizationReasons

As per chat w/ @JDutil on IRC

Also fix similar ReimbursementType migration

Fixes #5154
RMA form fix and cancel fix

- Remove form field when the return item cannot be added.  Looks weird and it also causes nested attributes to raise.
- Cancel associated return items when canceling an RMA.  Return Item validations will ensure they can be canceled.

Fixes #5156