Update icon only once

We have multiple LoadIconTasks started for the same icon, first from the
list view measurement and then from the actual view biding. We let all
those tasks to update the UI which riggered (through an observed but not
precicly comprehended mechanism) multiple announcements for the first
item in the list.
Ideally, we should have only one loading task for an item, but that
would be a more complex fix. Instead, we just let the winning task to
update the UI.

Fix: 238681660
Test: Manual test.
Change-Id: I8cc7a9a12a3b2e9e49834500d8b7d2bf3e6367d3