Do not add effort command interface for GZ sim (#355)

gz_ros2_control seems to not cope fine with having the effort
command interface. As this is only an issue with Humble (Only tested with
GZ Sim Fortress), let's deactivate it in that case.

Author: urfeex

urdf/ur.ros2_control.xacro

@@ -69,7 +69,9 @@
       <joint name="${tf_prefix}shoulder_pan_joint">
         <command_interface name="position"/>
         <command_interface name="velocity"/>
-        <command_interface name="effort"/>
+        <xacro:unless value="$(arg sim_ignition)">
+          <command_interface name="effort"/>
+        </xacro:unless>
         <state_interface name="position">
           <!-- initial position for the FakeSystem and simulation -->
           <param name="initial_value">${initial_positions['shoulder_pan_joint']}</param>
@@ -80,7 +82,9 @@
       <joint name="${tf_prefix}shoulder_lift_joint">
         <command_interface name="position"/>
         <command_interface name="velocity"/>
-        <command_interface name="effort"/>
+        <xacro:unless value="$(arg sim_ignition)">
+          <command_interface name="effort"/>
+        </xacro:unless>
         <state_interface name="position">
           <!-- initial position for the FakeSystem and simulation -->
           <param name="initial_value">${initial_positions['shoulder_lift_joint']}</param>
@@ -91,7 +95,9 @@
       <joint name="${tf_prefix}elbow_joint">
         <command_interface name="position"/>
         <command_interface name="velocity"/>
-        <command_interface name="effort"/>
+        <xacro:unless value="$(arg sim_ignition)">
+          <command_interface name="effort"/>
+        </xacro:unless>
         <state_interface name="position">
           <!-- initial position for the FakeSystem and simulation -->
           <param name="initial_value">${initial_positions['elbow_joint']}</param>
@@ -102,7 +108,9 @@
       <joint name="${tf_prefix}wrist_1_joint">
         <command_interface name="position"/>
         <command_interface name="velocity"/>
-        <command_interface name="effort"/>
+        <xacro:unless value="$(arg sim_ignition)">
+          <command_interface name="effort"/>
+        </xacro:unless>
         <state_interface name="position">
           <!-- initial position for the FakeSystem and simulation -->
           <param name="initial_value">${initial_positions['wrist_1_joint']}</param>
@@ -113,7 +121,9 @@
       <joint name="${tf_prefix}wrist_2_joint">
         <command_interface name="position"/>
         <command_interface name="velocity"/>
-        <command_interface name="effort"/>
+        <xacro:unless value="$(arg sim_ignition)">
+          <command_interface name="effort"/>
+        </xacro:unless>
         <state_interface name="position">
           <!-- initial position for the FakeSystem and simulation -->
           <param name="initial_value">${initial_positions['wrist_2_joint']}</param>
@@ -124,7 +134,9 @@
       <joint name="${tf_prefix}wrist_3_joint">
         <command_interface name="position"/>
         <command_interface name="velocity"/>
-        <command_interface name="effort"/>
+        <xacro:unless value="$(arg sim_ignition)">
+          <command_interface name="effort"/>
+        </xacro:unless>
         <state_interface name="position">
           <!-- initial position for the FakeSystem and simulation -->
           <param name="initial_value">${initial_positions['wrist_3_joint']}</param>