webadmin,userportal: Fix client-side sort issue

This patch fixes an issue where items would disappear
from grid when activating client-side column sorting.

This patch does not attempt to guarantee stability of
sorting behavior in relation to fresh items retrieved
from server. In other words, following edge case:

a, apply client-side sorting on column A
b, apply client-side sorting on column B
c, refresh items, some items might switch positions

In future, we can improve sorting logic to guarantee
stability of sorting vs. refresh behavior.

Change-Id: I437e9dd7ff2afdb2d87fb0ba6c17dcb081cd965d
Signed-off-by: Vojtech Szocs <vszocs@redhat.com>
Signed-off-by: Lior Vernia <lvernia@redhat.com>