This caused the live XML to report the 'bridge' type instead of the
'network' type, which is a behavioural regression.
It also breaks 'virsh domif-setlink', 'virsh update-device' and
'virsh domiftune'
This reverts commit 518026e15959ab0e19b659a9f2ff502a54946498.
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>