Ensure taskbar visibility callbacks are called in init()

We're initializing the correct values, but the callback only runs if
the value is different than the default value of 0. Thus we weren't
updating the visibility according to the value 0 in init().

Test: Initialize taskbar while launcher is resumed
Fixes: 180103543
Change-Id: I3f754cac59e2bd5ad542de050e8b4c3146d5eebf