Add customer login url from Customer Url model to checkout config so …

[quisse]

…it contains the referer url if necessary

Description

Use the url created in the customer model instead of creating a new one with the url builder. The current way isn't adding a referrer parameter when required

Fixed Issues (if relevant)

1. Referer is not added to login url in checkout config #12627: Referer is not added to login url in checkout config

Manual testing scenarios

1. Enable Redirect Customer to Account Dashboard after Logging in in the Magento backend.
2. Retrieve the login url from the window.checkout object (key is customerLoginUrl)

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)

[omiroshnichenko]

Please, review comments in #12631