@Override
    public Object prepareValueForCache(RegionEntryContext context, Object value,
        boolean isEntryUpdate) {
      throw new IllegalStateException("Should never be called");
    }
Provides a dummy implementation of RegionEntry so that basicPut can return an instance that
make the upper levels think it did the put.
geode-core/src/main/java/org/apache/geode/internal/cache/ProxyRegionMap.java