Use L3 api from vpn ipsec driver via service plugin

VPNaaS and ML2 plugin won't work, because ML2 plugin
supports service version of L3.
In this commit, we modify ipsec driver to use L3 plugin.
This is also backward compatible change, because if L2 plugin
supports L3 get_service_plugin API returns L2 plugin.

Fixes bug 1238846

Change-Id: I36e541bb2e3e1df2e01f73a74f3e9005af6c38b7
Note: Exsiting unit test covers this change
(cherry picked from commit 8eb5735)

neutron/services/vpn/service_drivers/ipsec.py

@@ -21,6 +21,7 @@
 from neutron.openstack.common import log as logging
 from neutron.openstack.common import rpc
 from neutron.openstack.common.rpc import proxy
+from neutron.plugins.common import constants
 from neutron.services.vpn.common import topics
 from neutron.services.vpn import service_drivers
 
@@ -72,7 +73,8 @@ def _agent_notification(self, context, method, router_id,
         dispatch notification for the agent.
         """
         adminContext = context.is_admin and context or context.elevated()
-        plugin = manager.NeutronManager.get_plugin()
+        plugin = manager.NeutronManager.get_service_plugins().get(
+            constants.L3_ROUTER_NAT)
         if not version:
             version = self.RPC_API_VERSION
         l3_agents = plugin.get_l3_agents_hosting_routers(

neutron/tests/unit/services/vpn/service_drivers/test_ipsec.py

@@ -19,6 +19,7 @@
 
 from neutron import context
 from neutron.openstack.common import uuidutils
+from neutron.plugins.common import constants
 from neutron.services.vpn.service_drivers import ipsec as ipsec_driver
 from neutron.tests import base
 
@@ -46,8 +47,13 @@ def setUp(self):
         plugin_p = mock.patch('neutron.manager.NeutronManager.get_plugin')
         get_plugin = plugin_p.start()
         get_plugin.return_value = plugin
+        service_plugin_p = mock.patch(
+            'neutron.manager.NeutronManager.get_service_plugins')
+        get_service_plugin = service_plugin_p.start()
+        get_service_plugin.return_value = {constants.L3_ROUTER_NAT: plugin}
 
         service_plugin = mock.Mock()
+        service_plugin.get_l3_agents_hosting_routers.return_value = [l3_agent]
         service_plugin._get_vpnservice.return_value = {
             'router_id': _uuid()
         }