Load the URDF to the resource_manager before parsing it to CM (#262)

* Load the URDF to the resource_manager before parsing it to CM constructor (fixes ros-controls/ros2_control#1299)

(cherry picked from commit f5baf71)

gazebo_ros2_control/src/gazebo_ros2_control_plugin.cpp

@@ -275,6 +275,13 @@ void GazeboRosControlPlugin::Load(gazebo::physics::ModelPtr parent, sdf::Element
   std::unique_ptr<hardware_interface::ResourceManager> resource_manager_ =
     std::make_unique<hardware_interface::ResourceManager>();
 
+  try {
+    resource_manager_->load_urdf(urdf_string, false, false);
+  } catch (...) {
+    // This error should be normal as the resource manager is not supposed to load and initialize
+    // them
+    RCLCPP_ERROR(impl_->model_nh_->get_logger(), "Error initializing URDF to resource manager!");
+  }
   try {
     impl_->robot_hw_sim_loader_.reset(
       new pluginlib::ClassLoader<gazebo_ros2_control::GazeboSystemInterface>(