... when the system library is used.

Signed-off-by: Murilo Belluzzo <murilo.belluzzo@intel.com>

As the main repository for the librealsense recipe now contains
fixes required for linking catkin-based packages against it
we can stop maintaining our own version of librealsense recipe.

Also this patch adapts realsense-camera recipe to link against
the non-catkin version of librealsense.

Signed-off-by: Dmitry Rozhkov <dmitry.rozhkov@linux.intel.com>