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
Change RBD delete failure log level to warn

This is a recoverable issue in the backend, so we don't have to provide
the message on the error level.

Change-Id: I35711876b2c088ad28f32abd39248dc9a467d00d
Closes-Bug: #1256259
Merge "Change RBD delete failure log level to warn"
Merge "Segment LUN clones in NetApp iSCSI"
(Test commit) Change README to reflect Jio's fork of Cinder

Change-Id: I3f26c0a736e63725aec24ca2fa12c707b8e6460f