HiddenServiceStatistics gets set to 0 in your torrc, and stays 0 when you become a relay

HiddenServiceStatistics defaults to 1:

  V(HiddenServiceStatistics,     BOOL,     "1"),

but if you're not a public relay, it gets set to 0 on startup:

    if (!public_server_mode(options)) {
      options->CellStatistics = 0;
      options->EntryStatistics = 0;
      options->ConnDirectionStatistics = 0;
      options->HiddenServiceStatistics = 0;
      options->ExitPortStatistics = 0;
    }

and then when you saveconf, it doesn't match the default so you get a new line in your torrc file:

HiddenServiceStatistics 0

And then later if you run your Tor as a relay, it looks at the torrc file and decides not to collect or report hiddenservicestatistics, which is bad because that's supposed to be the default.

I think the fix is that we need an internal variable which reflects what we've decided to do, and we need to stop modifying the config option in place.

The same issue happened in legacy/trac#4244 (moved), and I think we have some other recent tickets to make this change for other config options.

This ticket would resolve legacy/trac#17909 (moved) as well.