[CentOS] (?) Mailman VERY slow with IPv6 (with work-around)

[Gordon Messmer]

> While testing I tried an strace of list_lists and found that it
> >was timing out on a read operation to a socket to the Avahi daemon
> >(/var/run/avahi-daemon/socket) while trying to resolve the
> >link-local IPv6 address.

Is avahi even installed by default on CentOS 7?  I don't see it 
installed on my lab's desktop systems, let alone servers.