Core accessibility settings should not be cleared on restore.

1. The core accessibility settings required for a blind user to use
   the device should not be overwritten on restore. There could have
   been enabled via a global gesture from setup wizard, hence the
   user definitely needs them. Restoring disabled values for these
   settings render the device useless unless sighted help is sought.

bug:7138401

Change-Id: Idc593889aa61fada65b0407623720517c827df53