Maybe check for GUARD_WAIT circuit readiness whenever a guard fails
Right now we check whether any
GUARD_WAIT circuits can become usable (
OPEN) once a second or so, in
circuit_upgrade_circuits_from_guard_wait(). But maybe we should do so more often -- possibly, whenever a guard is marked as down?
This would make some streams attach up to one second faster -- but only in the cases when primary guards are down but we expected them to be up.