webadmin: removing In-Use column from LUNs tables

Removing 'In Use' column from LUNs tables since its
meaning is confusing (relates only to the underline
LUN status).

Change-Id: I403079842e2ad44e925239cd0a1a2a93c4392b05
Signed-off-by: Daniel Erez <derez@redhat.com>