Clear parent wants focus on strong focus gain.

Some views (apparently ListView) will do synchronous layouting
of children an then request focus. In this scenario, the
requestee should clear parent wants-focus so that the parent
layout doesn't re-assign focus to itself.

Bug: 32072305
Test: android.widget.listview.focus.ListWithEditTextHeaderTest
Change-Id: Idac9a1401de9658a63c74ab72d20d2543a8ac83e