rqt_joint_trajectory_controller: Use urdf_parser

[christophfroehlich]

Maybe we can use the upstream urdf_parser_py? The mentioned issue got fixed years ago..

ros2_controllers/rqt_joint_trajectory_controller/rqt_joint_trajectory_controller/joint_limits_urdf.py

Lines 17 to 20 in 925a690

	# TODO: Use urdf_parser_py.urdf instead. I gave it a try, but got
	# Exception: Required attribute not set in XML: upper
	# upper is an optional attribute, so I don't understand what's going on
	# See comments in https://github.com./ros/urdfdom/issues/36

[bailaC]

Hello @christophfroehlich , are we going to do this work? If yes, I can give it a try.

[christophfroehlich]

no one is working on that afaik. Thanks for picking this.
I just had the idea when we were fixing a bug. Please check if it really makes sense/supports all we need before you start coding!