When circuit times are fixed, they can't be "relaxed"

In legacy/trac#28639 (moved), we had trouble diagnosing a sbws bug. tor said that circuit times were "relaxed", even when LearnCircuitBuildTimeout was 0.

When circuit_build_times_disabled() is true, we should change these log messages so that they make sense: https://github.com/torproject/tor/blob/b058f64cc002b44e6dd48616ca3163a01c3f3e14/src/core/or/circuituse.c#L591

I think relaxed_timeout is meaningless when circuit_build_times_disabled() is true, but that's another issue.