Make sure max_corner_v2 is fully calculated before proactively
flushing moves from the lookahead queue. Without this, some moves
would do unnecessary pressure advance during cornering.
Also, handle the min/max_corner_v2 calculations correctly in the rare
case where a move that does only acceleration is immediately followed
by a move that does only deceleration.
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>