Save region correctly to save sales address from admin [backport]

[raumatbel]

Related with PR#11381

Description

Save region correctly to save sales address from admin

Fixed Issues (if relevant)

1. State/Province Not displayed after edit Billing Address on Sales Orders - Backend Admin. #10441: State/Province Not displayed after edit Billing Address on Sales Orders - Backend Admin.

Steps to reproduce

1. Go to the backend -> Sales -> Orders -> View any order.
2. Select the section -> Information -> Address Information
3. Edit Billing Address, for example the street address.
4. Save Order Address.

Note: The same issue happen with the Shipping Address.

Manual testing scenarios

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)