Libvirtd has long had integration with avahi for advertising libvirtd
using mDNS when TCP/TLS listening is enabled. For a long time the
virt-manager application had support for auto-detecting libvirtds
on the local network using mDNS, but this was removed last year

  commit fc8f8d5d7e3ba80a0771df19cf20e84a05ed2422
  Author: Cole Robinson <crobinso@redhat.com>
  Date:   Sat Oct 6 20:55:31 2018 -0400

    connect: Drop avahi support

    Libvirtd can advertise itself over avahi. The feature is disabled by
    default though and in practice I hear of no one actually using it
    and frankly I don't think it's all that useful

    The 'Open Connection' wizard has a disproportionate amount of code
    devoted to this feature, but I don't think it's useful or worth
    maintaining, so let's drop it

I've never heard of any other applications having support for using
mDNS to detect libvirtd instances. Though it is theoretically possible
something exists out there, it is clearly going to be a niche use case
in the virt ecosystem as a whole.

By removing avahi integration we can cut down the dependency chain for
the basic libvirtd install and reduce our code maint burden.
Reviewed-by: NJán Tomko <jtomko@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

Validate that the virNetServer(Client) RPC APIs are processing the
private data callbacks correctly by passing in non-NULL pointers.
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

Rename the test to virnetdaemontest and use virNetDaemon objects instead
of virNetServer inside.
Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>

The virNetServer class has the ability to serialize its state
to a JSON file, and then re-load that data after an in-place
execve() call to re-connect to active file handles. This data
format is critical ABI that must have compatibility across
releases, so it should be tested...