message: fixup! Unify real-world and Gazebo URDF descriptions
diff: />
  <xacro:if value="$(arg hand)">
  - <xacro:gazebo-joint joint="${prefix}finger_joint1" transmission="hardware_interface/EffortJointInterface" />
  - <xacro:gazebo-joint joint="${prefix}finger_joint2" transmission="hardware_interface/EffortJointInterface" />
  + <xacro:gazebo-joint joint="$(arg arm_id)_finger_joint1" transmission="hardware_interface/EffortJointInterface" />
  + <xacro:gazebo-joint joint="$(arg arm_id)_finger_joint2" transmission="hardware_interface/EffortJointInterface" />
  <!-- Friction specific material for Rubber/Rubber contact -->
  - <xacro:gazebo-friction link="${prefix}leftfinger" mu="1.13" />
  - <xacro:gazebo-friction link="${prefix}rightfinger" mu="1.13" />
  + <xacro:gazebo-friction link="$(arg arm_id)_leftfinger" mu="1.13" />
  + <xacro:gazebo-friction link="$(arg arm_id)_rightfinger" mu="1.13" />
  </xacro:if>
  <gazebo>
  