fixup, fail on bots

td.FailStep() isn't enough to fail the bot,
so go back to a call to td.Fatal() when failures>0.

Change-Id: Ib2be7b15200376ab8a16e4a1b69d98fde0630673
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/364471
Reviewed-by: Mike Klein <mtklein@google.com>
1 file changed