Support cloning from one dataset/root on a pool to a different dataset/root on the same pool

**Describe the problem/challenge you have**
Currently [there's a strict equality check done](https://github.com/openebs/zfs-localpv/blob/3192ca432d3b0bb6abbbdd30273040743b6d911c/pkg/driver/controller.go#L416) but I think as far as ZFS is concerned only the root pool has to be the same.


**Describe the solution you'd like**
The check should compare the pool, i.e. whatever is before the slash.
