redis usage is broken

[John-Colvin]

The mistake was introduced here: https://github.com/rejectedsoftware/userman/commit/acbe674e3695df79b0ddafd68f55cee8cb4be7e1#diff-3e3173a50db7d7cd7e3561efce0f0e8aR68

The problem is that for e.g. http://127.0.0.1:8765/1 InetPath produces path segments ["", "1"], so getting the first one and converting to long doesn't work.

I don't know whether this is a bug in InetPath or in userman, but it completely breaks userman w/ redis.