Update example to avoid breaking when run against Redis 3.0.

[ci skip]

examples/custom_cluster_distributor.php

@@ -84,6 +84,11 @@ for ($i = 0; $i < 100; $i++) {
 $server1 = $client->getClientFor('first')->info();
 $server2 = $client->getClientFor('second')->info();
 
+if (isset($server1['Keyspace'], $server2['Keyspace'])) {
+    $server1 = $server1['Keyspace'];
+    $server2 = $server2['Keyspace'];
+}
+
 printf("Server '%s' has %d keys while server '%s' has %d keys.\n",
     'first', $server1['db15']['keys'], 'second', $server2['db15']['keys']
 );