Currently in burn_in_tests.py evergreen yaml configuration file location is hardcoded
https://github.com/mongodb/mongo/blob/1382877972003390495e3dfe261ef368e24be163/buildscripts/burn_in_tests.py#L45

Therefore we are not able to generate burn-in for etc/evergreen_nightly.yml project.

We should make evergreen yaml file location configurable and can also default it to etc/evergreen.yml for backward compatibility.