[CT] Re-enable parallel runs to test different fixes
[CT] Re-enable parallel runs to test different fixes

BUG=skia:
TBR=benjaminwagner

Review URL: https://codereview.chromium.org/1822313002

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot