Stabilize Travis CI integration tests suite

[ishakhsuvarov]

Description

Travis CI integration test suites for 2.3-develop branch are frequently failing with timeout on integration batch 2. This is caused by incorrect distribution of the tests across suites, where suite 1 runs for just 11 minutes, and suite 2 runs for up to 50 minutes.

This Pull Request changes this distribution to spread execution time more evenly between batches 1, 2 and 3.

Reference build result: https://travis-ci.org/ishakhsuvarov/magento2/builds/405247843

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 @ishakhsuvarov. Thank you for your contribution
Here is some useful tips how you can test your changes using Magento test environment.
Add the comment under your pull request to deploy test or vanilla Magento instance:

• @magento-engcom-team give me test instance - deploy test instance based on PR changes
• @magento-engcom-team give me {$VERSION} instance - deploy vanilla Magento instance

For more details, please, review the Magento Contributor Assistant documentation

[osrecio]

Hi @ishakhsuvarov , I'm checking this PR, seems like is ok. I have it the same problems in some PR. Thanks!

[magento-engcom-team]

Hi @ishakhsuvarov. Thank you for your contribution.
We will aim to release these changes as part of 2.3.0.
Please check the release notes for final confirmation.