AVP demo on sim: unclear which parking stalls can be goal
Description
This is created as a result of manual testing (#926 (comment 558325690)) done on April 22, 2021
How to Reproduce
Run AVP demo on lgsvl following this article
Current Behavior
When selecting some parking stalls as the goal in rviz resulted in the vehicle not moving at all.
@JWhitleyWork mentioned that only certain parking stalls are guaranteed to work for the demo and only those should be used. The documentation does not make this clear and also these stalls are hard to find on rviz.
Expected behavior
Documentation should make it clear which stalls are allowed to be chosen as the goal points. Also, these stalls should be easy to find on rviz with the instructions in the article.