GEODE-6007: Fix missing servers_ variable (#519)

Authored-by Michael Oleske <moleske@pivotal.io>
diff --git a/clicache/integration-test2/Cluster.cs b/clicache/integration-test2/Cluster.cs
index 8ccfe00..8ceb219 100644
--- a/clicache/integration-test2/Cluster.cs
+++ b/clicache/integration-test2/Cluster.cs
@@ -32,6 +32,7 @@
         private int serverCount_;
         private bool started_;
         private List<Locator> locators_;
+        private List<Server> servers_;
         private string name_;
         internal int jmxManagerPort = Framework.FreeTcpPort();
         internal string keyStore_ = Environment.CurrentDirectory + "/ServerSslKeys/server_keystore.jks";