Adds V3 API specific urlmap tests

Adds V3 API versions of the urlmap unittests. These test that
the V3 content is returned when expected in the format expected.

Adds the extension plugin as being discoverage in the fake policy
files for the unitests to provide some easily known data to check
for the urlmap tests.

Updates extension info api sample tests

Partially implements v3-api-unittests

Change-Id: I67f2a3516ffee02b6dbf258ee35e1fd084ba060c

doc/v3/api_samples/extension-info/extensions-list-resp.json

@@ -1,5 +1,12 @@
 {
     "extensions": [
+        {
+            "alias": "extensions",
+            "description": "Extension information.",
+            "name": "extensions",
+            "namespace": "http://docs.openstack.org/compute/core/extension_info/api/v3",
+            "version": 1
+        },
         {
             "alias": "flavors",
             "description": "Flavors Extension.",

doc/v3/api_samples/extension-info/extensions-list-resp.xml

@@ -1,5 +1,8 @@
 <?xml version='1.0' encoding='UTF-8'?>
 <extensions xmlns:atom="http://www.w3.org/2005/Atom" xmlns="http://docs.openstack.org/common/api/v1.0">
+  <extension alias="extensions" version="1" namespace="http://docs.openstack.org/compute/core/extension_info/api/v3" name="extensions">
+    <description>Extension information.</description>
+  </extension>
   <extension alias="flavors" version="1" namespace="http://docs.openstack.org/compute/core/flavors/v3" name="flavors">
     <description>Flavors Extension.</description>
   </extension>