[apic_aim] ML2Plus SubnetPool and AddressScope support

Add mechanism driver and extension driver support the the SubnetPool
and AddressScope resources, including ensure_tenant.

Change-Id: Icb00eb223d1e503f946ffba54de51e89ba260a1d

gbpservice/neutron/plugins/ml2plus/patch_neutron.py

@@ -0,0 +1,32 @@
+# Copyright (c) 2016 Cisco Systems Inc.
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from neutron.api import extensions
+
+from gbpservice.neutron.plugins.ml2plus import extension_overrides
+
+# Monkeypatch Neutron to allow overriding its own extension
+# descriptors. Note that extension descriptor classes cannot be
+# monkeypatched directly because they are loaded explicitly by file
+# name and then used immediately.
+
+_real_get_extensions_path = extensions.get_extensions_path
+
+
+def get_extensions_path(service_plugins=None):
+    path = _real_get_extensions_path(service_plugins)
+    return extension_overrides.__path__[0] + ':' + path
+
+extensions.get_extensions_path = get_extensions_path