BackupManagerService uses BackupManagerConstants.

This change update the backup manager service to use newly created
BackupManagerConstants for some configuration parameters.

This is part 2 of the change.

Test: Used 'adb logcat -b system' to verify the settings worked.
Bug: 63351792
Change-Id: Ia6c9a2afbbaf3481a742a67c48ce9995c1ce6483