Remove hardcoded localhost from ZK test

Zookeeper test container should not be using localhost
Gerrit CI build slaves are ephemeral docker containers that
could run on a different host.

Change-Id: If6de3eb017691c8133a8812278c803a63789526d
diff --git a/src/test/java/com/googlesource/gerrit/plugins/multisite/validation/dfsrefdb/zookeeper/ZookeeperTestContainerSupport.java b/src/test/java/com/googlesource/gerrit/plugins/multisite/validation/dfsrefdb/zookeeper/ZookeeperTestContainerSupport.java
index db8fe5a..7b9ebb5 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/multisite/validation/dfsrefdb/zookeeper/ZookeeperTestContainerSupport.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/multisite/validation/dfsrefdb/zookeeper/ZookeeperTestContainerSupport.java
@@ -73,7 +73,7 @@
     container.start();
     Integer zkHostPort = container.getMappedPort(2181);
     Config splitBrainconfig = new Config();
-    String connectString = "localhost:" + zkHostPort;
+    String connectString = container.getContainerIpAddress() + ":" + zkHostPort;
     splitBrainconfig.setBoolean("ref-database", null, "enabled", true);
     splitBrainconfig.setString("ref-database", "zookeeper", "connectString", connectString);
     splitBrainconfig.setString(