Cloning breaks when there's a ZFS property set on the StorageClass.

[datamattsson]

When cloning a dataset from a StorageClass that have ZFS dataset modifiers like compression set, the clone fails.

22:15:35 client.go:168: response: 500 Internal Server Error, length=144
22:15:35 client.go:138: status code was 500 Internal Server Error for request: action=POST path=http://unix/VolumeDriver.Create, attempting to decode error response.
22:15:35 dockervol.go:273: unable to create/update docker volume using general-4892aaeb-fd92-11e8-8147-000c2966ae98 & map[allowOverrides:description compression:lz4 description:My MariaDB Clone Claim size:1 cloneOf:general-3e16ba7d-fd92-11e8-8147-000c2966ae98 mountConflictDelay:30] - status code was 500 Internal Server Error for request: action=POST path=http://unix/VolumeDriver.Create, attempting to decode error response response - &{{  map[]} this property can not be modified for snapshots: tank/k8s/general-3e16ba7d-fd92-11e8-8147-000c2966ae98@2018-12-11T22:15:35.966178582Z}