Camera: Disable HDR when scene mode is other than auto

- HDR option is enabled even when scene mode is not auto.
  Due to this preview and snapshot are still remain in previous
  scene mode after enabling HDR.

- Fix is to disable the HDR when scene mode is other than auto.

Change-Id: Icec96816a7ed6f3daacc8b79841dee5db6b4b04a
CRs-Fixed: 648847
Camera2: Still popup tips when change scene to other after turn off HDR

The toast popup or not depend on the value of hdr and scene mode,
but now the value mHdrOn status is not uniform with the actual hdr
value, which lead to popup toast incorrect.

Get the value of scene mode or hdr from the preference directly rather
than a new variable. So the mHdrOn is not used and delete it.

CRs-Fixed: 674521

Change-Id: I1c6926e0ba295e9869109b7412a7413323d3bd1c
Camera: open Camera and start Preview in a seperate thread.

Start openCamera and start preview in a separate thread so that
UI initialization and preview can run parallely. This is to
improve camera cold start latency.

Change-Id: I57af45bc90a4db1630c73449d543c3ff0992e55c
Merge commit 'refs/changes/47/74747/4' of http://review.cyanogenmod.org/CyanogenMod/android_packages_apps_Camera2 into cm-11.0