Generate JSON with mDNS entries only when built --with-avahi
Generate JSON with mDNS entries only when built --with-avahi

One string was already used only if that condition was true, second one
is added now.  Both are used in a nicer way.

Signed-off-by: Martin Kletzander <e82f23e74d43760279ebcc505dac4ae70d5627d0@redhat.com>

jfehlig/libvirt,zippy2/libvirt,jardasgit/libvirt,datto/libvirt,taget/libvirt,fabianfreyer/libvirt,libvirt/libvirt,jfehlig/libvirt,andreabolognani/libvirt,rlaager/libvirt,zippy2/libvirt,crobinso/libvirt,nertpinx/libvirt,andreabolognani/libvirt,jardasgit/libvirt,nertpinx/libvirt,datto/libvirt,fabianfreyer/libvirt,crobinso/libvirt,taget/libvirt,taget/libvirt,datto/libvirt,crobinso/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,jardasgit/libvirt,eskultety/libvirt,jfehlig/libvirt,agx/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,taget/libvirt,agx/libvirt,olafhering/libvirt,agx/libvirt,agx/libvirt,andreabolognani/libvirt,libvirt/libvirt,VenkatDatta/libvirt,rlaager/libvirt,eskultety/libvirt,VenkatDatta/libvirt,eskultety/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,olafhering/libvirt,zippy2/libvirt,nertpinx/libvirt,andreabolognani/libvirt,agx/libvirt,rlaager/libvirt,rlaager/libvirt,taget/libvirt,olafhering/libvirt,olafhering/libvirt,VenkatDatta/libvirt,libvirt/libvirt,eskultety/libvirt,zippy2/libvirt,jfehlig/libvirt,datto/libvirt,eskultety/libvirt,rlaager/libvirt,crobinso/libvirt,nertpinx/libvirt,jardasgit/libvirt,datto/libvirt,libvirt/libvirt