Restart nodes in dtests

.java

@Test
public void works() throws Throwable
{
    try (Cluster cluster = init(Cluster.build(3).start()))
    {
        cluster.get(2).shutdown();
        cluster.get(2).startup();
        cluster.get(3).shutdown();
        cluster.get(3).startup();
    }
}

@Test
public void fails() throws Throwable
{
    try (Cluster cluster = init(Cluster.build(3).start()))
    {
        cluster.get(2).shutdown();
        cluster.get(3).shutdown();
        cluster.get(2).startup();
        cluster.get(3).startup();
    }
}