This should have no effect on the bitstream format (see also no related
encoder change). This is like moving code from the top of the loop to
the bottom of the loop.

This change allows us to:
* Make sure we consume the final renormalization byte after the last
symbol in an ANS partition.
* Move back toward a single renormalization operation for some ANS modes
since we know the bounds of the state mutation algorithm that got us out
of the valid state range.

Change-Id: Ia80246fd0ed805aa61b913a362546b3f08e4d79c