lzc_rollback_to() should support rolling back to a clone's origin.
The current checks in zfs_ioc_rollback() would not allow that because the
origin snapshot belongs to a different filesystem.
The overly restrictive check was introduced in 7600, but it was not a
regression as none of the existing tools provided a way to rollback to the
origin.

EINVAL is returned when a dataset does not have any snapshots, so there is
nothing to roll back to.
Although the code in zfs_do_rollback checks for that condition in advance, it's
still possible that the snapshot(s) gets removed after the check and before the
rollback sync task is executed.
At the moment zfs command would crash when that happens.