Make it possible to listen on unix:// addresses, not only tcp sockets

Although by default redoctober should listen on TCP port, there is no reason why it shouldn't be able to listen on unix socket or unix abstract socket. With this patch one can supply "tcp://", "tcp6://", "tcp4://", or "unix://" prefix to the address and do just that.

To use abstract unix sockets you'd need to give option with @ sign: "-addr unix://@abstract_socket".