game: fix think/physics step mismatch problem

whenever we step physics we MUST step everything else
but render. Otherwise we'll get problems in case if
think component manipulates impulses/forces of an object
continously. The problem is that think component doesn't know in
advance how much physics steps will happen, so it can't predict
the state of an object, thus, it can't do certain things reliably,
such as path-following, keeping constant speed, constant
direction, etc.