ogre_helpers: Fixing mesh memory leak
ogre_helpers: Fixing mesh memory leak

This fixes a memory leak which is caused due to no meshes ever being
destroyed without removing the mesh from the mesh manager.
This gets really bad when drawing meshes with 50K triangles at 10Hz,
resulting in a leak rate @ ~60MB/sec.

ros-visualization/rviz,ros-visualization/rviz,ros-visualization/rviz,ros-visualization/rviz,ros-visualization/rviz