Order address edition from the backend disables the "region" field

[vincentwinkel]

Preconditions

1. Magento CE 2.0.9 without sample data is installed
2. Also tested on CE 2.0.7

Steps to reproduce

1. In backend, go to Sales > Orders
2. Choose an order (not shipped I guess) with at least one address (billing or shipping) containing the "region" field set
3. Edit this address (changing fields or not doesn't matter)
4. Save

Expected result

1. The address must be correctly set, with the "region" field

Actual result

1. The "region" field disappears. But if you edit again, the select is correctly set on the good value, because the "region_id" field still exists, instead of the "region" field which is empty
   

[olysenko]

Hi,
this issue duplicates #4000. Fix was delivered into develop branch.