Fix for New OMPL virtual function breaks build

I have not tested this at runtime but it does compile. 

Based on https://github.com/ros-planning/moveit_planners/pull/32

Issue https://github.com/ros-planning/moveit_planners/issues/31
We don't actually need this check. For older versions of OMPL, this will simply be a function that exists in MoveIt, but is not called by OMPL.