Cache Setting values

Cache the Settings values by reading these values from Setting from disk
 to prevent disk I/O access during the API calling. This is based on an
 assumption that the Settings system will itself cache this value after
 the first read and thus only the first read after boot will access the
 disk.

Test: Treehugger
Bug: 148081953
Change-Id: Ia934d013b3643872677cd764865a1ae07eaa7ba7