Set objects indirection API in network service

We need to set the
nova.objects.baseNovaObject.indirection_api global inside the network
service to point to the conductor API so that the object actions will
 be done by RPC to conductor.

Part of blueprint: nova-network-objects

Change-Id: I9e2c643eae7d09f5037485386e6ea53b75587980
Sync module units from oslo

Module units landed in Nova first, then was accepted by oslo with
minor changes. This patch removes nova specific unit module and
test, replaces with module units in oslo.

commit in Oslo:'Add unit constants' f9308560c36918cc

Change-Id: I6054c18a56f59d33a69f4714be19d34fbe9de335
Co-Authored-By: Sahid Orentino Ferdjaoui <sahid.ferdjaoui@cloudwatt.com>
Merge "Sync module units from oslo"
Merge "Set objects indirection API in network service"