[autoroll] Fix roll result for abandoned dry runs
[autoroll] Fix roll result for abandoned dry runs

When a new commit lands, we abandon the active dry run, regardless of
its result, but we're throwing away the dry run success/failure result
and just using the result we get from Gerrit when we pull down the CL,
which for abandoned CLs is always failure.

Bug: skia:
Change-Id: I0d77bc8a35cd1f153bd398baa824f42a1c5150f4
Reviewed-on: https://skia-review.googlesource.com/25320
Commit-Queue: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>
Reviewed-by: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>

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