Run mesos-dns via Marathon

[jonas]

Motivation

Better visibility on failures.

Input

• GCE tutorial: http://mesosphere.github.io/mesos-dns/docs/tutorial-gce.html
• Apollo DCOS role: https://github.com/Capgemini/Apollo/tree/master/roles/dcos_cli

Output

• Updated Mesos DNS role that
  -- Generates marathon template with proper hostname constraints and instances
  -- Deploys or updates the marathon template

Test

• Mesos DNS is shown in Marathon UI
• SSHing into any node and running dig master.mesos should show IP of a master node