Close model (multilogin)

[ovvn]

model.close = function (cb) {
  cb = this.wrapCallback(cb);
  var model = this;
  this.whenNothingPending(function() {
    model.root.socket.close();
    cb();
  });
}

In some places were we create a model from a backend manually we leave an opened socket. This PR closes open socket connections in the places.