wait_closed issue on freebsd

[robertsdotpm]

It seems like if you call close() on a loop.create_server object and then await wait_closed with the expectation that afterwards the connection_lost function will have been called then this doesn't seem to be the case on FreeBSD (or maybe the case in general.)

It would be easy to fix this by patching the custom BaseProto's close to await a future that gets set on connection_lost? Something like that.