private static void unregisterKey(Object key) {
    try {
      unregisterKeyOnly(key);
    } catch (Exception ex) {
      Assert.fail("failed while un-registering key(" + key + ")", ex);
    }
  }
exercises the ClientSession interface to register interest in a server on behalf of a client

@param clientId the DM of the client
@param key the key that the client is interested in
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/tier/sockets/InterestListDUnitTest.java