Camera: Discard AutoFocus ioctl if camera preview is not running

Auto focus ioctls should be issued only when camera preview is
running. Added lock for start preview, stop preview and start
auto focus for mCameraRunning. Added null check for finding
auto focus mode

Change-Id: I0d2f2d458822bf988f2815de5c0871222b020f9a
CRs-Fixed: 232916
2 files changed