Add support for deprecated configuration vars in Juno

Just like the beginning of every other release, remove the deprecated
config option aliases that were marked as deprecated in Icehouse.

Nova patch - https://review.openstack.org/#/c/88456/

Change-Id: Idd051c516002030e8e191c7b8d31f1ff408e1c7d
diff --git a/lib/neutron b/lib/neutron
index 9e1e787..15cfa8e 100644
--- a/lib/neutron
+++ b/lib/neutron
@@ -316,7 +316,7 @@
     # set NOVA_VIF_DRIVER and optionally set options in nova_conf
     neutron_plugin_create_nova_conf
 
-    iniset $NOVA_CONF DEFAULT libvirt_vif_driver "$NOVA_VIF_DRIVER"
+    iniset $NOVA_CONF libvirt vif_driver "$NOVA_VIF_DRIVER"
     iniset $NOVA_CONF DEFAULT linuxnet_interface_driver "$LINUXNET_VIF_DRIVER"
     if is_service_enabled q-meta; then
         iniset $NOVA_CONF DEFAULT service_neutron_metadata_proxy "True"