Allow one-hop directory fetching circuits the full "circuit build timeout"
period, rather than just half of it, before failing them and marking
the relay down. This fix should help reduce cases where clients declare
relays (or worse, bridges) unreachable because the TLS handshake takes
a few seconds to complete.
Fixes bug 6743 (one piece of bug 3443); bugfix on 0.2.2.2-alpha, where
we changed the timeout from a static 30 seconds.
