Fixup IPv6 iBFT interface description

The kernel iBFT implementation had an issue with IPv6 addresses,
which required the implementation of an additional 'prefix-len'
parameter.
This patch updates the open-iscsi code to use and display this
attribute if present.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Updated changes file for last patch from Hannes