Add Server.iter_connections_async() analogous to Connection.iter_messages_async. Change STOP_ON.CONN_CLOSED to STOP_ON.CLOSED because it is now applicable to former as well as latter.
Add Server.iter_connections_async() analogous to Connection.iter_messages_async.
Change STOP_ON.CONN_CLOSED to STOP_ON.CLOSED because it is now applicable
to former as well as latter.

ldo/dbussy