Fix default controller in common launchfile

As mentioned in #206 this lists a non-existing controller

Author: Felix Exner

ur_robot_driver/launch/ur_control.launch

@@ -13,7 +13,7 @@
   <arg name="script_sender_port" default="50002" doc="The driver will offer an interface to receive the program's URScript on this port. If the robot cannot connect to this port, `External Control` will stop immediately."/>
   <arg name="kinematics_config" doc="Kinematics config file used for calibration correction. This will be used to verify the robot's calibration is matching the robot_description. Pass the same config file that is passed to the robot_description."/>
   <arg name="tf_prefix" default="" doc="tf_prefix used for the robot."/>
-  <arg name="controllers" default="joint_state_controller vel_based_pos_joint_traj_controller force_torque_sensor_controller robot_status_controller"/>
+  <arg name="controllers" default="joint_state_controller scaled_pos_joint_traj_controller force_torque_sensor_controller robot_status_controller"/>
   <arg name="stopped_controllers" default="joint_group_vel_controller"/>
   <arg name="urscript_file" default="$(find ur_robot_driver)/resources/ros_control.urscript" doc="Path to URScript that will be sent to the robot and that forms the main control program."/>
   <arg name="rtde_output_recipe_file" default="$(find ur_robot_driver)/resources/rtde_output_recipe.txt" doc="Recipe file used for the RTDE-outputs. Only change this if you know what you're doing."/>