Missing [all] sections inside the sample (#3500)

* Missing [all] sections inside the sample

* Update hosts.ini

inventory/sample/hosts.ini

 # ## Configure 'ip' variable to bind kubernetes services on a
 # ## different ip than the default iface
 # ## We should set etcd_member_name for etcd cluster. The node that is not a etcd member do not need to set the value, or can set the empty string value.
+[all]
 # node1 ansible_host=95.54.0.12  # ip=10.3.0.1 etcd_member_name=etcd1
 # node2 ansible_host=95.54.0.13  # ip=10.3.0.2 etcd_member_name=etcd2
 # node3 ansible_host=95.54.0.14  # ip=10.3.0.3 etcd_member_name=etcd3
@@ -11,16 +12,16 @@
 # ## configure a bastion host if your nodes are not directly reachable
 # bastion ansible_host=x.x.x.x ansible_user=some_user
 
-# [kube-master]
+[kube-master]
 # node1
 # node2
 
-# [etcd]
+[etcd]
 # node1
 # node2
 # node3
 
-# [kube-node]
+[kube-node]
 # node2
 # node3
 # node4