zfs mounts used size not always correctly reported

I've notices that the reporting on zfs pools is not accurate. The used value for each is not correct as can be seen here:

```
|system/logs |zfs | |301Mi| 9% -----|3.1Gi| 3.4Gi|/var/log
|system/audit |zfs | |301Mi| 9% -----|3.1Gi| 3.4Gi|/var/log/audit
|system/home |zfs | |170Mi| 5% -----|3.1Gi| 3.3Gi|/home
```
`zfs list` show the used as:
```
NAME USED AVAIL REFER MOUNTPOINT
system/audit 25.2M 3.14G 25.2M /var/log/audit
system/home 170M 3.14G 170M /home
system/logs 301M 3.14G 301M /var/log
```
It seems to catch the 301M for `/var/log` and apply it to `/var/log/audit` too.

Start by reproducing the discrepancy with the issue's `zfs list` output and compare it with dysk's filesystem rows for `/var/log`, `/var/log/audit`, and `/home`. Trace the filesystem reporting path that gathers ZFS mount values; done means each dataset row reports its own used value rather than reusing the parent mount's value.

Written by the indexing model from the issue text.