Cannot set physics parameters using ROS parameters

[stertingen]

Affects gazebo_ros_api_plugin.

Description

It's impossible to set physics parameters like sor_pgs_w via roslaunch parameters due to the initial override of the dynamic reconfigure parameters in https://github.com/ros-simulation/gazebo_ros_pkgs/blob/kinetic-devel/gazebo_ros/src/gazebo_ros_api_plugin.cpp#L2216.

To Reproduce

Steps to reproduce the behavior:

1. Create launchfile:

   <launch>
   <include file="$(find gazebo_ros)/launch/empty_world.launch" />
   <rosparam param="gazebo">
   sor_pgs_w: 1.0
   </rosparam>
   </launch>

2. Launch above launchfile
3. Execute rosparam get /gazebo/sor_pgs_w
4. See that the value has the default value 1.3

Expected behavior

I expected to read the value 1.0 as it is explicitly set it in above launchfile

Environment (please complete the following information):

• OS: Ubuntu 16.04
• Gazebo version: Gazebo 7
• ROS version: Kinetic Kame
• gazebo_ros_pkgs: 2.5.19-1xenial-20200109-045116+0000
• glx server in use: (not relevant)

[stertingen]

However, there's a workaround using dynparam:

<launch>
  <include file="$(find gazebo_ros)/launch/empty_world.launch" />
  <node name="gazebo_physics_config" pkg="dynamic_reconfigure" type="dynparam" args="set_from_parameters gazebo">
    <rosparam>
      sor_pgs_w: 1.0
    </rosparam>
  </node>
</launch>