release(3.2.4): add the Python agent parity fixes to the 3.2.4 CHANGELOG #38

The 3.2.4 CHANGELOG section covers the Redis persistence fix only. The reference parity fixes merged after it (#37: rules refresh gate, wall-clock key stamp, autoFlushRunning stat) ship in the same 3.2.4 release, so I add them to that section. The version is already 3.2.4 and no v3.2.4 tag exists yet.