message: determine link_name from arm_id in cartesian_impedance_example_controller.launch
diff: <node name="controller_spawner" pkg="controller_manager" type="spawner" respawn="false" output="screen" args="cartesian_impedance_example_controller"/>
  <node pkg="rviz" type="rviz" output="screen" name="rviz" args="-d $(find franka_example_controllers)/launch/rviz/franka_description_with_marker.rviz"/>
  <node name="interactive_marker" pkg="franka_example_controllers" type="interactive_marker.py" required="true" output="screen">
  - <param name="link_name" value="panda_link0" />
  + <param name="link_name" value="$(arg arm_id)_link0" />
  <remap from="equilibrium_pose" to="/cartesian_impedance_example_controller/equilibrium_pose" />
  </node>
  <node name="rqt_reconfigure" pkg="rqt_reconfigure" type="rqt_reconfigure" required="false" />
  