Throttle and retry

[kit-klein]

When a client is making rapid requests to a device it will often result in ClientError exceptions.

Upon investigation this is occurring for a two reasons.

1. Multiple async requests can happen in parallel and overload the comms stack of the device. When this happens, the device will start resetting TCP connections - resulting in the exception. To avoid this we now use a semaphore to throttle requests such that they are limited to 3 at once.

2. aiohttp will reuse sockets for multiple http requests. It appears a race condition can occur where the HA client attempts to send a TCP payload after the device has closed the connection via a FIN. When this happens the device will immediately reset the connection. To handle this each method now performs retries - in testing this completely mitigated the problem.

In addition to the enhancements above I formatted (black) and linted (flake8) the file.

[heythisisnate]

this looks good! thanks