Federated authentication via ECP functional tests

Adds a first test for the federated authentication feature. It handles
first the authentication using the SAML2 ECP profile.

The tests cleanup have some issues, see related bug.

Related-Bug: 1642692
Change-Id: I3b393a695c6d9f846efdaf302c1beea34e6bd54b
diff --git a/keystone_tempest_plugin/plugin.py b/keystone_tempest_plugin/plugin.py
index 9fe67e8..9311409 100644
--- a/keystone_tempest_plugin/plugin.py
+++ b/keystone_tempest_plugin/plugin.py
@@ -33,7 +33,15 @@
     def register_opts(self, conf):
         config.register_opt_group(conf, project_config.identity_group,
                                   project_config.IdentityGroup)
+        config.register_opt_group(conf, project_config.identity_feature_group,
+                                  project_config.IdentityFeatureGroup)
+        config.register_opt_group(conf, project_config.fed_scenario_group,
+                                  project_config.FedScenarioGroup)
 
     def get_opt_lists(self):
         return [(project_config.identity_group.name,
-                 project_config.IdentityGroup)]
+                 project_config.IdentityGroup),
+                (project_config.identity_feature_group.name,
+                 project_config.IdentityFeatureGroup),
+                (project_config.fed_scenario_group.name,
+                 project_config.FedScenarioGroup)]