[Backport] Fixes #18357 - SQL error when table prefix used.

[gelanivishal]

Original PR

#18412

Description

Hard-coded table names cause errors if a table prefix, passing the table name to getTable resolves this.

Fixed Issues (if relevant)

1. checkout_agreement_store doesn't exist #18357
   Magento 2.2.6 Terms and Conditions are Not visible in Admin #18954

Manual testing scenarios

1. Create a store using table prefixes
2. Navigate to Store > Terms and Conditions in the admin backend
3. Without the patch, errors are generated

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-engcom-team]

Hi @gelanivishal. Thank you for your contribution
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[gelanivishal]

@VladimirZaets I can't find any Codacy/PR Quality Review error. Can you processed this PR?

[magento-engcom-team]

Hi @sidolov, thank you for the review.
ENGCOM-3989 has been created to process this Pull Request

[ghost]

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[Ctucker9233]

@magento-engcom-team Why was this moved from the 2.2.8 release to 2.2.9? It seems like a simple fix that should be released asap as it has caused many including myself significant problems.