Fixes for parameter declarations (#879)

Without these changes, I've been seeing lots of 'foo has already been
declared' errors.

nav2_dwb_controller/dwb_core/include/dwb_core/trajectory_critic.hpp

@@ -99,7 +99,9 @@ public:
     name_ = name;
     costmap_ros_ = costmap_ros;
     nh_ = nh;
-    nh_->declare_parameter(name_ + ".scale", rclcpp::ParameterValue(1.0));
+    if (!nh_->has_parameter(name_ + ".scale")) {
+      nh_->declare_parameter(name_ + ".scale", rclcpp::ParameterValue(1.0));
+    }
     nh_->get_parameter(name_ + ".scale", scale_);
     onInit();
   }

nav2_dwb_controller/dwb_critics/src/twirling.cpp

@@ -39,7 +39,9 @@ namespace dwb_critics
 {
 void TwirlingCritic::onInit()
 {
-  nh_->declare_parameter(name_ + ".scale", rclcpp::ParameterValue(0.0));
+  if (!nh_->has_parameter(name_ + ".scale")) {
+    nh_->declare_parameter(name_ + ".scale", rclcpp::ParameterValue(0.0));
+  }
 
   // Scale is set to 0 by default, so if it was not set otherwise, set to 0
   nh_->get_parameter(name_ + ".scale", scale_);

nav2_dwb_controller/nav_2d_utils/include/nav_2d_utils/parameters.hpp

@@ -143,18 +143,15 @@ void moveParameter(
 {
   param_t value;
   if (nh->get_parameter(current_name, value)) {
-    // TODO(crdelsey): What's the ROS 2 equivalent of deleteParam?
-    // if (should_delete)
-    //   nh->deleteParam(old_name);
+    if (should_delete) {nh->undeclare_parameter(old_name);}
     return;
   }
   if (nh->get_parameter(old_name, value)) {
-    // TODO(crdelsey): What's the ROS 2 equivalent of deleteParam?
-    // if (should_delete) nh->deleteParam(old_name);
+    if (should_delete) {nh->undeclare_parameter(old_name);}
   } else {
     value = default_value;
   }
-  nh->set_parameters({rclcpp::Parameter(current_name, value)});
+  nh->set_parameter(rclcpp::Parameter(current_name, value));
 }