progress: tweak how os.Stderr is mocked
#2812
| Job | Run time |
|---|---|
| 2m 55s | |
| 5s | |
| 2h 9m 10s | |
| 2h 12m 10s |
os.Stderr is mocked
#2812
| Job | Run time |
|---|---|
| 2m 55s | |
| 5s | |
| 2h 9m 10s | |
| 2h 12m 10s |