[SERVICE] constraint supports

[anak10thn]

https://docs.docker.com/engine/reference/commandline/service_create/#/specify-service-constraints---constraint use :

services:
   app:
       image: "aksaramaya/docker-http-server:v1"
       constraint: "node.role==manager"

node	attribute matches	example
node.id	node ID	node.id == 2ivku8v2gvtg4
node.hostname	node hostname	node.hostname != node-2
node.role	node role: manager	node.role == manager
node.labels	user defined node labels	node.labels.security == high
engine.labels	Docker Engine’s labels	engine.labels.operatingsystem == ubuntu 14.04