A11y voice and switch access on seekbar

Tapping on seek bar will click on the middle of seekbar, but we cannot
remove seekbar from a11y focus because it is being used by switch access
to slide forward or backward and also because this will be against
requirements. We need to let a11y able to use all UI components
available on the screen.

Flag: NONE
Bug: 317170527
Bug: 320416792
Test: Checked UI and made sure switch access works fine. Also, voice
access is able to tap on the seekbar. UI works perfectly fine without
a11y as well.

Change-Id: I3673f5762f6682a0908a07f9da0c6eecf553fc9d