Be more verbose when warning about not finding a circuit ID

On IRC:

"[WARN] failed to get unique circID. [99 duplicates hidden] [WARN] No unused circ IDs. Failing.

24/7 for days now. filling up the logs quite fast. Deosnt seem to have any effect on the relays speed. didnt find any solid explanation for what causes this error.

[WARN] failed to get unique circID. then this [WARN] No unused circ IDs. Failing."

It is hard to say why this error occurs without more verbose logging output.