private static void destroyKeys(List keys) {
    Region r = cache.getRegion(REGION_NAME);
    for (Object key : keys) {
      r.destroy(key);
    }
  }
unregister a key for a particular client in the server

@param clientId the client's ID
@param key the key it's no longer interest in
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/tier/sockets/InterestListDUnitTest.java