The validation of iscsi session should be case insensitive since IPv6
address is case insensitive. If the portal address are all lower cases,
and the address get from 'iscsiadm -m session' contain upper cases,
the validation of iscsi session will failed, the loop will be endless.
Change-Id: Ief5108e40f13cc53d8d9e9c5d1a5054f58f72aa0
Closes-bug: #1793627
(cherry picked from commit 8782c4accf)
(cherry picked from commit e01e5db822)