zfs mounts used size not always correctly reported

[daniejstriata]

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.