Set cluster ID when ZK connection state is connected

The master and agent process check they can connect to ZooKeeper with a cluster
ID value. This cluster ID value is passed in as a CLI switch on startup. The
code also checks the cluster ID ZK node exists and stores it in an
`AtomicBoolean`.

The `AtomicBoolean` is updated with a `org.apache.zookeeper.Watcher` on the
node itself and with a `ConnectionStateListener` that updates when the
connection state to ZK changes.

My hypothesis is that when agents lose connection entirely to the ZKs and the
connection then comes back, the `ConnectionState` is `CONNECTED` instead of
`RECONNECTED`. This would skip the conditional and the `AtomicBoolean` wouldn't
get updated.

Helios agents that do not automatically recover have these logs for
`ConnectionState`.  Notice that the last state is `CONNECTED`.

```
dxia@bad-host:~$ grep 'DefaultZooKeeperClient connection state change' /path/to/helios/info.log
2019-09-19T01:53:14.391+00:00 bad-host helios[21939]: DefaultZooKeeperClient connection state change - SUSPENDED
2019-09-19T01:53:33.511+00:00 bad-host helios[21939]: DefaultZooKeeperClient connection state change - LOST
2019-09-19T01:54:15.333+00:00 bad-host helios[21939]: DefaultZooKeeperClient connection state change - RECONNECTED
2019-09-19T03:15:16.298+00:00 bad-host helios[21939]: DefaultZooKeeperClient connection state change - SUSPENDED
2019-09-19T03:15:39.592+00:00 bad-host helios[21939]: DefaultZooKeeperClient connection state change - LOST
2019-09-19T08:11:09.721+00:00 bad-host helios[15902]: DefaultZooKeeperClient connection state change - CONNECTED
```

There are some helios agents that were fine that also had `CONNECTED` as the
last state in the logs though.

But it seems like we should update the `AtomicBoolean` in cases of
`CONNECTED`, `RECONNECTED`, and `READ_ONLY`.

helios-services/src/main/java/com/spotify/helios/servicescommon/coordination/DefaultZooKeeperClient.java

@@ -96,7 +96,7 @@ public void process(WatchedEvent event) {
       @Override
       public void stateChanged(CuratorFramework client, ConnectionState newState) {
         log.info("DefaultZooKeeperClient connection state change - {}", newState);
-        if (newState == ConnectionState.RECONNECTED) {
+        if (newState.isConnected()) {
           checkClusterIdExists(clusterId, "connectionStateListener");
         }
       }