Don't cache failed manual updates checks.
Review Request #3135 — Created June 2, 2012 and submitted
Don't cache failed manual updates checks. Once a thread finds that manual updates are required, that state is cached, requiring a restart to recompute the checks. This is particularly problematic when a thread happens to hit the database when it's temporarily down or something. Now, we only cache if checks pass, and not when they fail. If they fail, the next request will just try them again. That helps unstick these threads.
Site's checks seem to still work fine.