Only update local zss cache when Taskbar Toast already active.

Toast is handling suggestion updates itself during the session, and we
do not need to send along the new search suggestions passed from
bindExtraContainerItems. We should still store the updated suggestions
in memory for the next time Taskbar All Apps is invoked.

Test: Manual
Bug: 216683257
Flag: ENABLE_ALL_APPS_SEARCH_IN_TASKBAR
Flag: ZERO_STATE_WEB_DATA_LOADER
Change-Id: I68673e5941dc4b81c3e72b7ec579f566f13ee4d2