Correct Zookeeper stack example to work with a user-defined network

zookeeper/stack.yml

@@ -9,7 +9,7 @@ services:
       - 2181:2181
     environment:
       ZOO_MY_ID: 1
-      ZOO_SERVERS: server.1=zoo1:2888:3888 server.2=zoo2:2888:3888 server.3=zoo3:2888:3888
+      ZOO_SERVERS: server.1=0.0.0.0:2888:3888 server.2=zoo2:2888:3888 server.3=zoo3:2888:3888
 
   zoo2:
     image: zookeeper
@@ -19,7 +19,7 @@ services:
       - 2182:2181
     environment:
       ZOO_MY_ID: 2
-      ZOO_SERVERS: server.1=zoo1:2888:3888 server.2=zoo2:2888:3888 server.3=zoo3:2888:3888
+      ZOO_SERVERS: server.1=zoo1:2888:3888 server.2=0.0.0.0:2888:3888 server.3=zoo3:2888:3888
 
   zoo3:
     image: zookeeper
@@ -29,4 +29,4 @@ services:
       - 2183:2181
     environment:
       ZOO_MY_ID: 3
-      ZOO_SERVERS: server.1=zoo1:2888:3888 server.2=zoo2:2888:3888 server.3=zoo3:2888:3888
+      ZOO_SERVERS: server.1=zoo1:2888:3888 server.2=zoo2:2888:3888 server.3=0.0.0.0:2888:3888