Demote log warn about strange path lengths using congestion control
We discovered in Shadow logs that clients can create either 4-hop or 1-hop circuits that use congestion control. The code was emitting warn logs in these cases so we could monitor for it there more easily, but this issue is not warn-level serious.
The 1-hop cases are probably directory activity, hence those should just be info logs.
We have no idea how 4-hop Exit circuits can be created, but it is definitely happening (best guess: re-use of pre-built onion service circuits that happen to have Exit relays on them). Using these circuits won't break anything, but if those circuits get used for streams, they will be slower. So we will demote this warn to a notice.