Integration bridge has to be created

It is Openstack/Devstack requirement to have integration bridge (br-int) created on start.
It can be created manually, but there are situations when OVS console is not available. One of the way for getting through this is to write br-int switch into DS. This can be done by Neutron-Ovsdb bundle which listens on topology nodes in OPER DS. When a new node with OvsdbNodeAugmentation comes up and it has no reference to br-int, Neutron-Ovsdb should write this bridge into config DS.