Testing on another rate control patch reveals that in some
situations, where the encoder is flipping in and out of arf
mode, we get an encoder decoder mismatch.

Whilst it is still not clear why, skipping  the last buffer
update seems to trigger the problem. Until I can establish
why, or if there is another underlying cause, I am reverting
this change.

This reverts commit e5112b3a.

Change-Id: I315c5200414de89458015823344b7367e9dd75ba