In `set_max_file_descriptors()`, if `setrlimit()` fails, we log warn and bail out leaving the `max_out` pointer unset. It should be set to the current value returned by `getrlimit()` before we try to change it with `setrlimit()`. Flagging this as critical because right now on commit e48f8e5e87603812a6b1844a5fa27bbc44a3543e, if the ed25519_master_id_public_key can't be opened, tor shuts down.