fix(madsim): drop the future within the scope of TaskEnterGuard when a task is aborted
#918
| Job | Run time |
|---|---|
| 2m 25s | |
| 3m 56s | |
| 3m 19s | |
| 4m 9s | |
| 3m 48s | |
| 4m 11s | |
| 3m 53s | |
| 3m 32s | |
| 5m 12s | |
| 4m 32s | |
| 2m 11s | |
| 1m 15s | |
| 42m 23s |