Force gs.py to use generation rather than sequence-match.

Currently no consuming code has been found sans unittests so
this is reasonably safe.  For existing usage where it was
just a fail-if-exists check, the change restores functionality;
for any sequence tracking code (which I've yet to find sans locks
that don't use this pathway) it will break; it was broken via
the referenced bug anyways, thus is decided to move forward with.

BUG=chromium-os:37718
TEST=validation of the header, but nothing beyond that; TBR.

Change-Id: Ic1d42b0e9dca1be60105f86aa0eaaed6020e0f40
Previous-Reviewed-on: https://gerrit.chromium.org/gerrit/40929
(cherry picked from commit 114efcca9aca3e36ccac964b4b4a3768346ab799)
Previous-Reviewed-on: https://gerrit.chromium.org/gerrit/41106
Commit-Queue: Jon Salz <jsalz@chromium.org>
(cherry picked from commit e7089f2f6c3b557fc8aa83f2c8e3d11d8037fb4f)
Reviewed-on: https://gerrit.chromium.org/gerrit/41184
Reviewed-by: David James <davidjames@chromium.org>
Tested-by: David James <davidjames@chromium.org>
1 file changed