Stop adding a space when dumping an empty config value
We unconditionally add a space when dumping torrc files, even if there is no option value. (Which is rare, but does happen with some list options.)
The extra space is unnecessary and we should remove it.
This bug has been around since Tor 0.0.9pre6.
The fix is in this commit, I need to extract it and add a changes file: https://github.com/torproject/tor/pull/1477/commits/67d0178f1aba0a424364acc1c9f9dff2c72886a4