Fix for missing url_key after product import

[evilprophet]

Description

This fix will protect import for overwriting url_key when this is not specified in the import file.
$this->getUrlKey($rowData); This returns url_key when this is specified in the file or create it based on name, but in the situation when these 2 fields are missing in file empty string will be returned and used to overwrite url_key for imported products.

Fixed Issues (if relevant)

1. CSV Import of sku,attribute empties url_key value #17023>: CSV Import of sku,attribute empties url_key value

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)

[magento-cicd2]

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[magento-engcom-team]

Hi @evilprophet. Thank you for your contribution
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[nuzil]

@evilprophet thanks a lot for your contribution. This PR #17882 (review) looks more complete as its includes functionality to validate also "name" columns.