In the patch for BUG#21842, the code for handling old rows events were
refactored.  There were a bug in the refactored code (possibly introduced
after the patch for BUG#21842) that caused caused the refactored old events
to read a columns bitmap after image even though there is no such bitmap
for old events. As a result, the reading got out of sync, and started reading
invalid data.

This patch removes all trace of the after image column bitmap from the refactored
old events and removes functions that are no longer needed because they are empty.