fcache: duplicate FilterCacheInfo for FilterCacheRequest
fcache: duplicate FilterCacheInfo for FilterCacheRequest

A side effect of 87f945527fed269ae04eb199a06eb347061175ca was that
FilterCacheInfo was duplicated on the new pool; now that this is gone,
we must always duplicate it explicitly.

CM4all/beng-proxy,CM4all/beng-proxy,CM4all/beng-proxy,CM4all/beng-proxy,CM4all/beng-proxy,CM4all/beng-proxy