Clear accessibility focus when the window loses visibility

AccessibilityInteractionController checks window visibility during focus
search and when performing an action, which prevents the framework from
clearing focus when windows lose visibility. This change ensures that
focus will already have been cleared, which matches the behavior of the
other properties checked during focus search (view detachment and view
visibility).

Bug: 19169643
Change-Id: I795ed27ce8dfb7ecb1462943c81c5b14973a8d7a