Summary:
Instead of doing a cat for all the log files, we first sort them and by exit code and cat the failing tests at the end.
This will make it easier to debug failing tests, since we will just need to look at the end of the logs instead of searching in them

Test Plan: run it locally

Reviewers: sdong, yiwu, lightmark, kradhakrishnan, yhchiang, andrewkr

Reviewed By: andrewkr

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D62211