Bug#1053910: zfs: use zpool user properties instead of zfs user properties for scrub and trim cron scripts

[M. Zhou]

Source: zfs-linux
Version: 2.2.0-1~exp1
Severity: normal

zpool user property is supported now. We can use this feature for the
cron scripts instead of abusing the zfs user property at root dataset.
https://github.com/openzfs/zfs/pull/11680