add a a ros::spinOnce to get set_camera_info working
This is explained in the docs of CameraInfoManager
https://github.com/ros-perception/image_common/blob/hydro-devel/camera_info_manager/include/camera_info_manager/camera_info_manager.h#L71
Also, this fixes https://github.com/ros-perception/image_pipeline/issues/78
Merge pull request #13 from vrabaud/develop

add a a ros::spinOnce to get set_camera_info working