Add the ability to upload sky_tests to the flakiness dashboard.

Modify mojob.py to plumb through the arguments needed to upload
sky tests to the flakiness dashboard. A followup change will
need to modify the buildbot side to pass these arguments
to mojob.py.

R=abarth@chromium.org, jamesr@chromium.org

Review URL: https://codereview.chromium.org/726313007