/joint_states not published when loading multiple controllers simultaneously

[henningkayser]

When launching moveit_sim_controller with one active and one inactive controller (i.e. JointTrajectoryController and JointGroupPositionController) the JointStateController somehow fails to publish /joint_states. I think it's probably due to some racing condition. A simple workaround is to only spawn one controller and then to load the other with a small delay (~1-2 seconds).