Fix Respawn Velocity on Respawn Script

[Goldenheaven]

Fix rolling on respawn.

[Cheeseness]

Right now, this is happening because we spawn on a slope. This is going to end up being a normal situation though (if we do cart destruction and respawns at arbitrary points on the map), so a solution here might be nice.

Perhaps once we implement #158, having that apply on spawn and be removed once the player moves might be a good option.