Fix the version discovery document

In Queens the API version discovery document did not include the
"links" section. This is causing problems with newer versions of the
openstacksdk.
This patch addes the "links" section to the version discovery document.

Change-Id: Id791339a912a15aa6dded31ce22baedb253c78a0
Story: 2004368
Task: 27970

octavia/api/root_controller.py

@@ -15,6 +15,7 @@
 import logging
 
 from oslo_config import cfg
+from pecan import request as pecan_request
 from pecan import rest
 from wsme import types as wtypes
 from wsmeext import pecan as wsme_pecan
@@ -33,33 +34,49 @@ class RootController(rest.RestController):
 
     def __init__(self):
         super(RootController, self).__init__()
-        self._versions = []
-        v1_enabled = CONF.api_settings.api_v1_enabled
-        v2_enabled = CONF.api_settings.api_v2_enabled
-        if v1_enabled:
+        self.v1_enabled = CONF.api_settings.api_v1_enabled
+        self.v2_enabled = CONF.api_settings.api_v2_enabled
+        if self.v1_enabled:
             self.v1 = v1_controller.V1Controller()
-            self._versions.append(
-                {
-                    'status': 'SUPPORTED',
-                    'updated': '2014-12-11T00:00:00Z',
-                    'id': 'v1'
-                })
-        if v2_enabled:
+        if self.v2_enabled:
             setattr(self, 'v2.0', v2_controller.V2Controller())
-            self._versions.append(
-                {
-                    'status': 'CURRENT',
-                    'updated': '2017-06-22T00:00:00Z',
-                    'id': 'v2.0'
-                })
-        if not (v1_enabled or v2_enabled):
+        if not (self.v1_enabled or self.v2_enabled):
             LOG.warning("Both v1 and v2.0 API endpoints are disabled -- is "
                         "this intentional?")
-        elif v1_enabled and v2_enabled:
+        elif self.v1_enabled and self.v2_enabled:
             LOG.warning("Both v1 and v2.0 API endpoints are enabled -- it is "
                         "a security risk to expose the v1 endpoint publicly,"
                         "so please make sure access to it is secured.")
 
     @wsme_pecan.wsexpose(wtypes.text)
     def get(self):
-        return {'versions': self._versions}
+        host_url = pecan_request.path_url
+
+        if not host_url.endswith('/'):
+            host_url = '{}/'.format(host_url)
+
+        versions = []
+        if CONF.api_settings.api_v1_enabled:
+            versions.append(
+                {
+                    'status': 'SUPPORTED',
+                    'updated': '2014-12-11T00:00:00Z',
+                    'id': 'v1',
+                    'links': [{
+                        'href': host_url + 'v1',
+                        'rel': 'self'
+                    }]
+                })
+        if CONF.api_settings.api_v2_enabled:
+            versions.append(
+                {
+                    'status': 'CURRENT',
+                    'updated': '2017-06-22T00:00:00Z',
+                    'id': 'v2.0',
+                    'links': [{
+                        'href': host_url + 'v2.0',
+                        'rel': 'self'
+                    }]
+                })
+
+        return {'versions': versions}