Latest ros2_control mock hardware setup has deprecated xacro parameters

[sea-bass]

I just tested out the 2023-06-29 ROS Humble snapshot and (surprise!) ros2_control has introduced another incompatibility with mock hardware, it seems.

[ros2_control_node-2] [INFO] [1689026791.796165788] [resource_manager]: Loading hardware 'ur5e' 
[ros2_control_node-2] [INFO] [1689026791.797834110] [resource_manager]: Initialize hardware 'ur5e' 
[ros2_control_node-2] [WARN] [1689026791.797878390] [mock_generic_system]: Parameter 'fake_sensor_commands' has been deprecated from usage. Use'mock_sensor_commands' instead.
[ros2_control_node-2] [WARN] [1689026791.797894218] [mock_generic_system]: Parsing of optional initial interface values failed or uses a deprecated format. Add initial values for every state interface in the ros2_control.xacro. For example: 
[ros2_control_node-2] <state_interface name="velocity"> 
[ros2_control_node-2]   <param name="initial_value">0.0</param> 
[ros2_control_node-2] </state_interface>

Tracking down the changelist, I suspect it has to do with ros-controls/ros2_control#1051

[fmauch]

This should be fixed in #920