Currently, all intermediate results from Browsertime are being written to the artifact folder: https://dxr.mozilla.org/mozilla-central/source/testing/raptor/raptor/browsertime/base.py#46-48

This means that if they aren't deleted before the end of the run due to a failure, then they get uploaded and bring in a lot of noise to the artifact view in treeherder. See this job for instance: https://treeherder.mozilla.org/#/jobs?repo=try&tier=1%2C2%2C3&revision=84f69eb32aaf4bec9ba8c11724dbd9de3842169c&selectedJob=288405967

We should either move the tarring to before any exit calls, or change the result dir to a temporary directory that is then archived and placed in the artifact upload folder: https://dxr.mozilla.org/mozilla-central/source/testing/raptor/raptor/raptor.py#172-179

In our current case, we risk hitting issues like bug 1595715 again.