pods allow duplicate endpoint ports

[jdef]

this can lead to confusing/surprising results w/ respect to service discovery. we strictly forbid this via validation.

for example:

{
  "id": "/nginx",
  "containers": [
    {
      "name": "container-1",
      "resources": { "cpus": 1, "mem": 128 },
      "endpoints": [
        {
          "name": "http",
          "containerPort": 80,
          "hostPort": 0,
          "protocol": [ "tcp" ],
          "labels": { "VIP_0": "1.1.1.1:80" }
        },
        {
          "name": "httpp",
          "containerPort": 80,
          "hostPort": 0,
          "protocol": [ "tcp" ],
          "labels": { "VIP_0": "1.1.1.1:80" }
        }
      ],
      "image": { "id": "nginx", "kind": "DOCKER" }
    }
  ],
  "scaling": { "kind": "fixed", "instances": 1 },
  "networks": [ { "name": "dcos", "mode": "container" } ]
}

[aquamatthias]

Path is here: https://phabricator.mesosphere.com/D496