Limit oscilation detection in the case where overshoot is very very
large.

This keeps the 9-bit cost patch from breaking the DownUp reisze test.
The patch pushed us to an 11% undershoot right before a scene cut
causing a 1200% overshoot. (Whereas before we were undershooting by
only 6% before overshooting by 1200%).

Change-Id: Id90ccfab8aba872ccadc45b73b3bb097b895677f