mlab-ns should report the test's port number

[mtlynch]

mlab-ns currently reports an HTTP port if the test supports a web interface / portal, but it doesn't report the port that the test actually listens on.

mlab-ns should add support in the database and the client response for the port that clients should use to connect to a particular test.

For example, something like:

{
  "city": "New York_NY",
  "url": "http://ndt.iupui.mlab1.lga03.measurement-lab.org:7123",
  "ip": [
    "64.86.148.139"
  ],
  "fqdn": "ndt.iupui.mlab1.lga03.measurement-lab.org",
  "tcp_port": 3001                     << add this to response
  "site": "lga03",
  "country": "US"
}