Update usage of "Swarm" for consistency

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

docs/reference/commandline/info.md

@@ -38,7 +38,7 @@ available on the volume where `/var/lib/docker` is mounted.
 ## Display Docker system information
 
 Here is a sample output for a daemon running on Ubuntu, using the overlay
-storage driver and a node that is part of a 2 node swarm cluster:
+storage driver and a node that is part of a 2-node swarm:
 
     $ docker -D info
     Containers: 14

docs/reference/commandline/node_demote.md

@@ -20,7 +20,7 @@ Options:
 
 ```
 
-Demotes an existing manager so that it is no longer a manager. This command targets a docker engine that is a manager in the swarm cluster.
+Demotes an existing manager so that it is no longer a manager. This command targets a docker engine that is a manager in the swarm.
 
 
 ```bash

docs/reference/commandline/node_promote.md

@@ -19,7 +19,7 @@ Options:
       --help   Print usage
 ```
 
-Promotes a node that is pending a promotion to manager. This command targets a docker engine that is a manager in the swarm cluster.
+Promotes a node to manager. This command targets a docker engine that is a manager in the swarm.
 
 
 ```bash

docs/reference/commandline/swarm_init.md

@@ -26,8 +26,8 @@ Options:
       --task-history-limit int          Task history retention limit (default 5)
 ```
 
-Initialize a swarm cluster. The docker engine targeted by this command becomes a manager
-in the newly created one node swarm cluster.
+Initialize a swarm. The docker engine targeted by this command becomes a manager
+in the newly created single-node swarm.
 
 
 ```bash

docs/reference/commandline/swarm_update.md

@@ -23,7 +23,7 @@ Options:
       --task-history-limit int          Task history retention limit (default 5)
 ```
 
-Updates a swarm cluster with new parameter values. This command must target a manager node.
+Updates a swarm with new parameter values. This command must target a manager node.
 
 
 ```bash