Remove release specific build image lookup.

Unrelated, safer check of build_log fields.

BUG=None
TEST=local run_generate.py runs.

Change-Id: I94a8d0b398ce7549af607027564655ddafbc9d6a
Reviewed-on: https://gerrit.chromium.org/gerrit/13090
Reviewed-by: Jim Hebert <jimhebert@chromium.org>
Commit-Ready: Mike Truty <truty@chromium.org>
Reviewed-by: Mike Truty <truty@chromium.org>
Tested-by: Mike Truty <truty@chromium.org>
3 files changed