cli: Change autolock flag description

This change incorporates feedback from @thaJeztah in the PR that added
the autolock flag. It changes the descriptions to be different for
"swarm init" and "swarm update" so that the boolean nature so that the
purpose of the flag in both contexts is clearer.

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>

command/swarm/update.go

@@ -25,6 +25,7 @@ func newUpdateCommand(dockerCli *command.DockerCli) *cobra.Command {
 		},
 	}
 
+	cmd.Flags().BoolVar(&opts.autolock, flagAutolock, false, "Change manager autolocking setting (true|false)")
 	addSwarmFlags(cmd.Flags(), &opts)
 	return cmd
 }