Tor 0.2.2 CBT notices are confusing users

Now that Tor 0.2.2 has gone stable, ordinary users are experiencing the log lines like:

    log_notice(LD_CIRC,
               "Based on %d circuit times, it looks like we don't need to "
               "wait so long for circuits to finish. We will now assume a "
               "circuit is too slow to use after waiting %ld seconds.",

We should turn as many of them into info lines as we can.