Until now, we have been using the default behaviour of async-broadcast
to await for active receivers (which translates to existance of any
message streams) when sending a message received on the socket. This has
been the right thing to do since otherwise, we'll needlessly keep
reading messages on the socket.

However, we are about to introduce multile broadcast channels in the
following commits and it wouldn't make sense to make active receivers of
one channel wait for active receivers on others.