void putExistingEntry(final InternalRegion owner, RegionEntry entry)
      throws RegionClearedException {
    putExistingEntry(owner, entry, false, null);
  }
If true (the default) then preserve old values in events. If false then mark non-null values as
being NOT_AVAILABLE.
geode-core/src/main/java/org/apache/geode/internal/cache/EntryEventImpl.java