Fix sonos async use

[MartinHjelmare]

Description:

• Entry setup wasn't using the async api. Fix this by using correct async api.
• Also use new async executor scheduler in async_added_to_hass.

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass

If the code does not interact with devices:

• Tests have been added to verify that the new code works.

[MartinHjelmare]

@amelchio I can't test this live. I've written a test that calls the scheduler and that works, but it doesn't really add so much since the incorrect previous usage doesn't fail that test. Not sure where we best should test this or how. I can push that commit with the test if we want.

[amelchio]

Looks good!

I tested your branch, it works with my Sonos setup.