Fix misleading proxy usage statistics message on launch

As soon as you launch the proxy it displays:

2022/03/23 09:27:18 In the last 1h0m0s, there were 0 connections. Traffic Relayed ↑ 0 B, ↓ 0 B.

I guess it will be better to don't display that until some time has actually passed. Or at least don't say In the last 1h, because it hasn't being running 1hour.