Make new-style single endpoint version discovery actually work for ironic

For (unclear) historical reasons the root single version endpoint also
contains "id" and "links" fields. This makes the current workaround
for old-style endpoints take priority over the correct algorithm.
This change reorders the code, so that if "version" is present, it
always take priority over the workaround.

The unit tests are updated to be closer to real output from ironic.

Change-Id: I743b954c6c5b2f986c213acb6ec6af7e08c9f5f8

keystoneauth1/discover.py

@@ -119,6 +119,13 @@ def get_version_data(session, url, authenticated=None):
         except KeyError:
             pass
 
+        # Otherwise if we query an endpoint like /v2.0 then we will get back
+        # just the one available version.
+        try:
+            return [body_resp['version']]
+        except KeyError:
+            pass
+
         # Older Ironic does not actually return a discovery document for the
         # single version discovery endpoint, which confuses the single-version
         # fallback logic. While there are no known other services returning
@@ -141,13 +148,6 @@ def get_version_data(session, url, authenticated=None):
                     body_resp.setdefault('version', resp.headers[header])
             return [body_resp]
 
-        # Otherwise if we query an endpoint like /v2.0 then we will get back
-        # just the one available version.
-        try:
-            return [body_resp['version']]
-        except KeyError:
-            pass
-
     err_text = resp.text[:50] + '...' if len(resp.text) > 50 else resp.text
     raise exceptions.DiscoveryFailure('Invalid Response - Bad version data '
                                       'returned: %s' % err_text)

keystoneauth1/tests/unit/test_discovery.py

@@ -590,11 +590,18 @@ class VersionDataTests(utils.TestCase):
             ironic_url, status_code=200,
             json={
                 'id': 'v1',
+                'version': {
+                    'id': 'v1',
+                    'links': [{
+                        "href": ironic_url,
+                        "rel": "self"}],
+                    'version': '1.40',
+                    'min_version': '1.10',
+                    'status': 'CURRENT',
+                },
                 'links': [{
                     "href": ironic_url,
                     "rel": "self"}],
-                'version': '1.40',
-                'min_version': '1.10',
             },
             # Keep headers so we can verify that body trumps headers
             headers={