Add driver names to a few flag descriptions to make is consistent

Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au>

drivers/openstack/openstack.go

@@ -176,7 +176,7 @@ func GetCreateFlags() []cli.Flag {
 		// the BoolFlag default value is always false
 		cli.StringFlag{
 			Name:  "openstack-docker-install",
-			Usage: "Set if docker have to be installed on the machine",
+			Usage: "Openstack should install docker on the machine",
 			Value: "true",
 		},
 	}