Tor should complain if the user has configured a too-short CBT
The reporter of legacy/trac#5363 set the following torrc lines, and Tor got flaky:
```
LearnCircuitBuildTimeout 0
CircuitBuildTimeout 5
```
Perhaps Tor should warn the user if he/she/it has specified a non-adaptive circuit-build timeout and Tor is failing to build too many circuits.
issue