A11Y - User switcher - Don't focus on Cancel button

It is the only item initially visible in the layout, and gets
focus and read by talkback. Initially hide all elements until
they views are bound, then set the visibility.

Fixes: 436691870
Test: talkback - launch from user switcher widget
Flag: EXEMPT bugfix
Change-Id: Ic358113c456c97fee7e1cf0d07f57366412abf29