Updated .gazebo files

config/pan_tilt_gazebo_config.yaml

 robotNamespace: ana/pan_tilt
+robotParam: robot_description
 

urdf/pan_tilt.gazebo

@@ -9,6 +9,7 @@
         <robotNamespace>/${properties['robotNamespace']}</robotNamespace>
         <controlPeriod>0.01</controlPeriod>
         <legacyModeNS>true</legacyModeNS>
+        <robotParam>/${properties['robotParam']}</robotParam>
       </plugin>
     </gazebo>