Fix for issue where trajectory_planner returns false to isGoalReached() even when internally it is done

When move_base calls isGoalReached() for trajectory_planner, the trajectory_planner's current implementation uses the base class method to return the value. However, this is sometimes different than what its control logic uses to decide at goal - causing move_base to recall the planner. This leads to the robot to turn towards the goal - stop and start turning the other direction (because it's given a new plan). 

Fix removes the call to the base class method - and returns a flag that is set in the control loop when the robot is within the tolerances.