Circular dependency between uuv_gazebo_ros_plugins and uuv_descriptions

[arturmiller]

The tests in uuv_gazebo_ros_plugins depend on uuv_descriptions (urdf_spawner is called in test_upload_default_fossen_vehicle.launch). However, in uuv_gazebo_ros_plugins a test_depend for uuv_descriptions is missing. I think the reason for that is, ROS would give a circular dependency warning. This is not only in general bad, but also blocks updating this project to the recent version of industrial_ci. I don't know exactly how this should be fixed, maybe urdf_spawner should be moved to somewhere else?