public void appendOldValueToMessage(EntryEventImpl event) {
      @Unretained
      Object val = event.getRawOldValue();
      if (val == null || val == Token.NOT_AVAILABLE || val == Token.REMOVED_PHASE1
          || val == Token.REMOVED_PHASE2 || val == Token.DESTROYED || val == Token.TOMBSTONE) {
        return;
      }
      event.exportOldValue(this);
    }
Add the cache event's old value to this message. We must propagate the old value when the
receiver is doing GII and has listeners (CQs) that require the old value.

@since GemFire 5.5
@param event the entry event that contains the old value
geode-core/src/main/java/org/apache/geode/internal/cache/DistributedCacheOperation.java