circuit: Avoid needless log info in circuit_get_best()
When looking for an introduction circuit in circuit_get_best(), we log an info
message if we are about to launch a new intro circuit in parallel. However,
the condition was considering marked for close circuit leading to the function
triggering the log info even though there is actually no valid intro circuit.
Signed-off-by: David Goulet <dgoulet@torproject.org>