Hey UDKAP,
In your level press P, this will highlight the navigation mesh, this is the area where the AI can walk. Then search in your world outliner for navmesh and click on: RecastNavmesh.
Now in the details panel of this try changing some of the values until you see the corners of the navmesh as sharp as possible.
I think this will get you closer to the behaviour that you want.
To do this right you need to change the pathfinding costs calculation but that is a bit harder.
Hope this helps 
Elias