Check if beekeeper is running before sending a request

Previously there were unambignous errors when
beekeeper was closed due to some reason.

In logs previously we could see:
- httpcore.UnsupportedProtocol: Request URL is missing an 'http://' or
  'https://' protocol.

Due to setting beekeeper webserver_http_endpoint to
`://0.0.0.0:0` when closing beekeeper because of some error.

Now there is a nice message about beekeeper not running.