hs: Memory leak in case of config failure

Very minor thing and thus why I think it is OK not to backport.

If the config_service() function fails, we fail to free the previously partitioned config line.

I found this by removing v2 support from tor and attempting to load a version 2 lead to this problem. It can also be triggered if HiddenServiceVersion is anything else than 2 or 3 at the moment.