datahopper_internal: Update the repos before doing a step.
datahopper_internal: Update the repos before doing a step.

Also drop the cache as it made the code more complex, and given the small number of commits we are dealing with it probably wasn't helping that much.

Review URL: https://codereview.chromium.org/1316453005

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