use swarm endpoint for controlling static slaves

In NXBT-2367 we've scripted static slaves update but we didn't take advantage of the swarm view for this. We should inter-operate with the swarm through it's single endpoint and let the swarm scheduling the containers according to nodes constraints (https://docs.docker.com/swarm/scheduler/filter/).

1. the list of slaves and their parameters will be saved in the code
2. the containers will register themselves into jenkins using the swarm mode
3. we could use the jenkins docker plugin for interacting with docker (no shell)
4. how connecting to the swarm, could require a dedicated slave – node('DOCKER-SWARM') { ... }