private static boolean poolReady(final PoolImpl pool) {
    try {
      Connection conn = pool.acquireConnection();
      // excuse = "acquireConnection returned null?";
      return conn != null;
    } catch (NoAvailableServersException e) {
      // excuse = "Cannot find a server: " + e;
      return false;
    }
  }
1. Invalidate a non-existent entry from the server. 2. Validate that the servers see after
invalidate. 3. Validate that the subscribed client invokes after invalidate.
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/tier/sockets/ClientServerForceInvalidateDUnitTest.java