MQE-1606: Mftf static check script should return error exit code when check fails

[tomreece]

Description

The static-checks command now returns 1 if any errors are found and 0 if there are no errors.

Fixed Issues (if relevant)

https://jira.corp.magento.com/browse/MQE-1606

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/verification tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)
• Changes to Framework doesn't have backward incompatible changes for tests or have related Pull Request with fixes to tests

[coveralls]

Coverage decreased (-1.6%) to 54.534% when pulling accceb8 on MQE-1606 into cd04795 on develop.

[KevinBKozan]

Changes are good, so good that they reveal the original implementation is a little off!
Fix the interface and the class to match your new pattern better, as it's a better design decision.

[tomreece]

@KevinBKozan -- I acted on your feedback and refactored a few minor things along the way. Let me know if I made things better or worse.