Allow concat fw-admin w/ other nets in serializer

For Neutron mode an orchestrator_serialiser does:
* Create a bridge 'br-fw-admin'
* Connect it to node.admin_interface
* It's allowed to connect other nets to node.admin_interface
* In GRE mode the bridge 'br-prv' is not created.
* Change an order of bridge creation to manadge right
  ordering of IP setup.
* Revert qickfixed changes in logic https://review.openstack.org/#/c/72563
* Revert qickfixed changes in verifying https://review.openstack.org/#/c/72606

Closes-bug: 1278363
Change-Id: I5a9036c61cdd0099a25cfc6c153f48d7f3e56876
Merge "Allow concat fw-admin w/ other nets in serializer"