It looks like your script is based on the sample moveit_ik_demo.py script described in Chapter 11.20 of ROS By Example Volume 2. I tested your script using the simulated Pi Robot arm after changing the target pose to be a valid pose for Pi Robot and the script works fine. So unfortunately I don't have an answer for you. Perhaps try posting your question to the MoveIt users group and be sure to include your launch file as well.
I'm not sure what you mean when you say "when simulating with ros_control". Can you please provide more details?
-- The Pi Robot Project http://www.pirobot.org/wordpress