Update visibility when attached

updateVisibility would normally be called during init, but a display or
font size change will have the same visibility before and after, so it
was being skipped. Instead let's just call it explicitly when the view
is attached

Fixes: 159646762
Test: atest KeyguardMediaControllerTest
Test: manual, change font size and observe no gap
Change-Id: Idad51d804c3e08ff673bea61924214a7ff6c0ccd