CHOMP: Fix handling of mimic joints (#3625)

As the CHOMP planner only considers active joints, it needs to use setJointGroupActivePositions()
instead of setJointGroupPositions().

moveit_planners/chomp/chomp_motion_planner/src/chomp_optimizer.cpp

@@ -952,7 +952,7 @@ void ChompOptimizer::setRobotStateFromPoint(ChompTrajectory& group_trajectory, i
   for (size_t j = 0; j < group_trajectory.getNumJoints(); ++j)
     joint_states.emplace_back(point(0, j));
 
-  state_.setJointGroupPositions(planning_group_, joint_states);
+  state_.setJointGroupActivePositions(planning_group_, joint_states);
   state_.update();
 }