Segment LUN clones in NetApp iSCSI

The NetApp ZAPI for clone_create and clone_start has a maximum size.
This fix breaks the lun into consumable sizes for the ZAPI.

Change-Id: Id4d0872c6099b7cfc73d806d772a3ae051a76b70
Closes-Bug: 1284182
(cherry picked from commit f0f52a0085a1f5bbd23e6cfa8f0ea935e8fd56c8)