Include test failure logs in step log when deflaking tests.

Test failures when deflaking do not report the failure logs
on trybots or CI bots. Add logs for failing tests when deflaking.

Bug: https://github.com/dart-lang/dart_ci/issues/160
Change-Id: I0ccb5bd3e4f7d19bd4dad42e91d1e9e2333c3e50
Reviewed-on: https://dart-review.googlesource.com/c/recipes/+/356820
Commit-Queue: William Hesse <whesse@google.com>
Reviewed-by: Alexander Thomas <athom@google.com>
18 files changed