cameraservice: Resolve message vs start/stop preview races

Move the mutex in start/stopPreview to include the metadata message
management. Fast start/stop sequences could (and would) eventually
cause the messages to be enabled/disabled out of sequence (or while
the camera wasn't ready for it)

Fixes BACON-173

Change-Id: I367bc45729ce2e858fea972f35e881a755c6021a
camera: Include camera parameters in device tree

Simple option to include camera parameters into your device tree.
All info can be seen here:
http://forum.xda-developers.com/android/help/dev-mod-to-add-extra-camera-parameters-t2814578

Change-Id: Ic5b27670fd0bb6ec11f6e902ce7ec3ca2ca10827