Make Nova_admin_tenant_id_setter notify neutron-server.

Add notification to ensure that changes in Nova_admin_tenant_id_setter
 will result with neutron-server restarting. This is necessary, otherwise
 it is possible for neutron.conf DEFAULT/nova_admin_tenant_id to not be set
 which will result in odd looking auth failures and cause instances to fail
 booting

Change-Id: Idbb2fe9ce63985e4236e41a642ef1b783bec3753
Closes-bug: #1343009
Merge "Make Nova_admin_tenant_id_setter notify neutron-server."