Should hopefully un-break#11800

#7439 added global caching of RBAC results.
Calls are cached based onhash(subject, object, action).
We often usedbauthz.AsSystemRestricted to handle "internal" authz calls, and these are often repeated with similar arguments and are likely to get cached.
So a transient error doing an authz check on a system function will be cached for up to a minute.
I'm just starting off with excludingcontext.Canceled but there's likely a whole suite of different errors we want to also exclude from the global cache.