Fixes #10255: base_shipping_discount_tax_compensation_amnt was empty from order onwards

[AntonEvers]

Description

Fixed Issues (if relevant)

1. Invoice grand_total and base_grand_total differ while in the same currency #10255: Invoice grand_total and base_grand_total differ while in the same currency

Manual testing scenarios

1. see Invoice grand_total and base_grand_total differ while in the same currency #10255 for testing scenario and MySQL dump file

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)

[AntonEvers]

Actually I wanted to rename the db fields from base_shipping_discount_tax_compensation_amnt to base_shipping_discount_tax_compensation_amount but that would be backward incompatible...

[orlangur]

Please check http://devdocs.magento.com/guides/v2.1/contributor-guide/backward-compatible-development/#allowed-code-changes out.

The constant will remain ugly BASE_SHIPPING_DISCOUNT_TAX_COMPENSATION_AMNT but the value and column name can be changed I believe. Unless it was shortened just because there is some limit on DB side or something.

[AntonEvers]

@orlangur do you still want me to change the amnt to amount? Even after this PR has been merged?

[orlangur]

I'm not sure why it was merged as is.

@ishakhsuvarov what do you think about #10435 (comment)? Maybe I'm missing something but if not let's do a fix the right way.