This moves the error-code check for verify-predictable mode to the API
method checking for status file outcomes, overwriting the default
behavior.

This is resembling the behavior prior to:
https://chromium-review.googlesource.com/c/808971/

Otherwise, the status file outcomes will expect some negative tests
to fail in the mozilla test suite, which pass in predictable mode.

Now, negative tests are simply not supported.

Bug: v8:7166
Change-Id: I1d4bcaf66cb54c5fbb217dd9091b88ecc5b0e456
Reviewed-on: https://chromium-review.googlesource.com/817741Reviewed-by: Sergiy Byelozyorov <sergiyb@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50110}