Fix chasing after Motion Manager & Pushing.

The motion manager introduced in rP25071 makes 'chasing' (e.g. an entity targeting another entity, which also applies to fleeing) behaviour symmetrical: both units see the initial state instead of it being ID-dependent.
This allows removing hacks introduced in rP24798 (and refined in rP24800).

Differential Revision: https://code.wildfiregames.com/D3785