frontend: Remove IteratorUtils class

Since we changed the items held in the ListModel from Iterable to
Collection, we can now remove IteratorUtils as it's redundant, instead of
iterating on the Iterable we can just use the size() method that Collection
object has

Change-Id: Iace61d708d6e66da4b898a6d6069136e1c838c4f
Signed-off-by: Tal Nisan <tnisan@redhat.com>