Fixes for HA 2016.6.6

[provinzio]

This PR fixes #34.

I am currently recieving the following error.
@binsentsu any ideas on this? I tried several things, but can not get rid of the warning. Everything else is working as expected.

2021-06-24 17:01:15 WARNING (MainThread) [homeassistant.components.mqtt.cover] Payload is not supported (e.g. open, closed, opening, closing, stopped): {"id":"0245f32c8f21","lastconnect":"2021-06-24T15:01:14.418Z","lastsuccess":"2021-06-24T15:01:15.728Z","lastaction":null,"state":"OPEN","battery":42,"light":7,"position":0}

I read things here, but couldn't derive a solution from that.

• https://community.home-assistant.io/t/payload-is-not-supported-e-g-open-closed-opening-closing-stopped-stop/306122/11
• https://www.home-assistant.io/integrations/cover.mqtt/#state_closed

[provinzio]

I was able to fix the warning 2021-06-24 17:01:15 WARNING (MainThread) [homeassistant.components.mqtt.cover] Payload is not supported (e.g. open, closed, opening, closing, stopped): {"id":"0245f32c8f21","lastconnect":"2021-06-24T15:01:14.418Z","lastsuccess":"2021-06-24T15:01:15.728Z","lastaction":null,"state":"OPEN","battery":42,"light":7,"position":0} with a trial end error approach.

I can rebase the commits if you like.
Otherwise, this is ready to be merged.