Make default nova_url use a version

The default nova_url for neutron is missing an API
version number. This can cause requests to fail
because the Nova /versions API cannot respond
to Neutron notification requests.

It seems reasonable for the default value to
at least have a chance at being correct so
this patch upgrades the default Nova API url to
use the Nova 'v2' API.

Related-bug: #1298640
Change-Id: Ib1449de84fbc01fb704ebfe4a016ac8f4932be96
(cherry picked from commit c09a14089a)

etc/neutron.conf

@@ -303,7 +303,7 @@ notification_driver = neutron.openstack.common.notifier.rpc_notifier
 # notify_nova_on_port_data_changes = True
 
 # URL for connection to nova (Only supports one nova region currently).
-# nova_url = http://127.0.0.1:8774
+# nova_url = http://127.0.0.1:8774/v2
 
 # Name of nova region to use. Useful if keystone manages more than one region
 # nova_region_name =

neutron/common/config.py

@@ -87,7 +87,7 @@ core_opts = [
                 help=_("Send notification to nova when port data (fixed_ips/"
                        "floatingip) changes so nova can update its cache.")),
     cfg.StrOpt('nova_url',
-               default='http://127.0.0.1:8774',
+               default='http://127.0.0.1:8774/v2',
                help=_('URL for connection to nova')),
     cfg.StrOpt('nova_admin_username',
                help=_('Username for connecting to nova in admin context')),