Always leave/reenter the top-most FSM state when SetNextState is called with the current FSM state.
When SetNextState is called with the current state, it will leave and re-enter so that any relevant cleanup will get called and things work as expected.
It will prevent possibly awkward code issues in UnitAI, which already called SetNextStateAlwaysEntering in a number of places to work around them.
This should most likely have been the default behaviour in the first place.
Reviewed By: Itms
Differential Revision: https://code.wildfiregames.com/D1488