nix-daemon: Disable path info cache

This is useless because the client also caches path info, and can
cause problems for long-running clients like hydra-queue-runner
(i.e. it may return cached info about paths that have been
garbage-collected).

src/libstore/store-api.cc

@@ -242,6 +242,7 @@ Path Store::computeStorePathForText(const string & name, const string & s,
 
 Store::Store(const Params & params)
     : storeDir(get(params, "store", settings.nixStore))
+    , state({std::stoi(get(params, "path-info-cache-size", "65536"))})
 {
 }