Don't call "miio.info" when a model was provided

[Algram]

This fixes #162.

The issue was that when you use a rooted vacuum with disabled access to the xiaomi cloud, a call to miio.info would fail. This PR checks if a model was provided via the options parameter already and if it was, skips the info enrichment.

You can test if this fix works for you aswell by providing the model in your options:
const device = await miio.device({ address: 'vacuum ip', token: 'vacuum token', model: 'rockrobo.vacuum.v1' })

[rytilahti]

This is a general problem with vacuums, rooted or not :-) Just wanted to add, that if you are running a rooted one, you can use https://github.com/dgiese/dustcloud/tree/master/dummycloud which makes info work.