Find out the state number for "Out of Service" in `lab.py`

[tianyizheng02]

In lab.py, the comments state that there are 4 possible states for lab computers: "off", "available", "in use", and "out of service". We know that the first three states correspond to 0, 1, and 2 in the JSON API data, but we don't know the number corresponding to "out of service", at least not for certain. Currently, the code looks like https://github.com/pittcsc/PittAPI/blob/684d056d362dbb1bb55b1176ee95b095d21bc597/pittapi/lab.py#L105-L113 and ideally we should have

for computer_info in lab_data["state"].values():
    if computer_info["up"] == 0:
        off_computers += 1
    elif computer_info["up"] == 1:
        available_computers += 1
    elif computer_info["up"] == 2:
        in_use_computers += 1
    elif computer_info["up"] == UNKNOWN:
        out_of_service_computers += 1
    else:
        # Raise some kind of error

We should figure out this number somehow. By documenting it, we can handle the "out of service" case correctly and also test the case.

[winterqt]

It's 3. From the keyserve client JS:

O = [
  {
    off: 'free used gone',
    on: 'down',
    order: '1'
  },
  {
    off: 'down used gone',
    on: 'free',
    order: '0'
  },
  {
    off: 'down free gone',
    on: 'used',
    order: '2'
  },
  {
    off: 'down free used',
    on: 'gone',
    order: '3'
  }
]

var C = O[P.up] || O[3]

up in the status dict is the index into O, so 3 is "gone", aka out of service.