Updates screen attention preference at onStart().

Screen attention preference needs to be refreshed at onStart() so that
it get updated immediately once the camera permission is revoked/granted
for the screen attention feature.

Bug: 171019472
Test: manual + atest AdaptiveSleepPreferenceControllerTest

Change-Id: If9ac68c022f10ffefde61b035bbf38ee14c02180
2 files changed