Data unavailable after restart when disk>ram

In class LoadStorageKVPairCallback:

bool retain = shouldBeResident();
if (!vb->ht.add(*i, false, retain))

{ getLogger()->log(EXTENSION_LOG_WARNING, NULL, "Failed to load item due to memory constraint.\n"); }

When that happens, we're pretty much in a bad state. We should abort or something here. (need a better test case)