Camera2: override Saturation&Contrast item when enable scence mode

When HDR or any other scene mode is enabled, should disable the
saturation and contrast items into gray.

( cherrypicked from commit aceeee3ef5812836265127ed784adb4ab5ed57fb )

Change-Id: Ia4e20e0ee2f80661c8b72bf81aeee6fa96dcdf1f
CRs-Fixed: 526617