Correct navbar colors after rebooting

System UI visibility flags shouldn't be set based on overlay
states. Overlays may persist across reboots leading to
situations where the navbar might be white when the rest of
the UI is black.

Change-Id: Id3d1e935c1f02a76491a92e521565468602719d5
Fixes: 63138897
Test: reboot, swipe up, look at navbar
(cherry picked from commit f7b7bab3)