Bug 1042866 — Add MCC/MNC in POST on mt/verify and use network-code for momt/verify

https://bugzilla.mozilla.org/show_bug.cgi?id=1042866
nit: put this into a new line (at the begining of the line?). e.g.

```js
sendError(
  res, 400,
  errors.INVALID_PARAMETERS,
  "Invalid MNC."
);
```