NetApp fix for 7mode iscsi volume stats

This fixes the bug for reporting correct
capacity information in case of 7mode
iscsi drivers.

Change-Id: Ie41009eca866830173809211d58470025be847e3
Closes-Bug: #1238967
(cherry picked from commit e4bde7adda4e885fe847e0bacc4d3fc84547e723)
Merge "NetApp fix for 7mode iscsi volume stats" into stable/havana