camera: Always enable preview metadata

 * Remove the ifdefs which enable/disable the preview metadata during
   start/stop preview.  This causes issues with face detection and
   other uses on new hardware.
 * I am not aware of any hardware which still needs this.

Change-Id: I3dd0941a61affb4862a2e8f4f0c2cf59c95b150e
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_frameworks_av into kk44