[MP] Fix crash on startup if r_DynamicGlow is 2
[MP] Fix some vehicles not showing up when spawned

The model name for the vehicle was being truncated so the server was
not able to register the vehicle's model correctly. This also caused
the client side to not show the model.
[MP] Moved console commands in the renderer to an array to avoid forgetting to remove commands at shutdowns.
Also refactored maxpolys/maxpolyverts initialization.