Add compute API response schema validation for 2.71

The 2.71 compute API includes the "server_groups" parameter
in the response to the following APIs:

- GET /servers/{server_id} (show)
- PUT /servers/{server_id} (update)
- POST /servers/{server_id}/action (rebuild)

This will be used in an upcoming change to test attaching
and detaching the root volume of a shelved offloaded instance.

Change-Id: I612a15c475404ded0af15b6241b9ac8ec9fb8e26
diff --git a/doc/source/microversion_testing.rst b/doc/source/microversion_testing.rst
index eaab168..b4f06e3 100644
--- a/doc/source/microversion_testing.rst
+++ b/doc/source/microversion_testing.rst
@@ -410,6 +410,10 @@
 
   .. _2.70: https://docs.openstack.org/nova/latest/reference/api-microversion-history.html#id63
 
+  * `2.71`_
+
+  .. _2.71: https://docs.openstack.org/nova/latest/reference/api-microversion-history.html#id64
+
 * Volume
 
   * `3.3`_