Return properly elevated context by get_admin_context() helper

In neutron_lib.context module there are two simple helper functions:
get_admin_context and get_admin_context_without_session.
Both returned Context object with is_admin=True but without admin role
set and due to that it wasn't proper admin context when new secure RBAC
policies are used.
With this patch both those helper functions returns properly elevated
Context object with admin role set.

Closes-Bug: #2015987
Change-Id: Ibde6acdb99555a6e43ca253523df7cbe4d150787

neutron_lib/context.py

@@ -176,13 +176,17 @@ class Context(ContextBaseWithSession):
 
 
 def get_admin_context():
+    # NOTE(slaweq): elevated() method will set is_admin=True but setting it
+    # explicity here will avoid checking in policy rules if is_admin should be
+    # set to True or not
     return Context(user_id=None,
                    tenant_id=None,
                    is_admin=True,
-                   overwrite=False)
+                   overwrite=False).elevated()
 
 
 def get_admin_context_without_session():
-    return ContextBase(user_id=None,
-                       tenant_id=None,
-                       is_admin=True)
+    # NOTE(slaweq): elevated() method will set is_admin=True but setting it
+    # explicity here will avoid checking in policy rules if is_admin should be
+    # set to True or not
+    return ContextBase(user_id=None, tenant_id=None, is_admin=True).elevated()

neutron_lib/tests/unit/test_context.py

@@ -143,6 +143,7 @@ class TestNeutronContext(_base.BaseTestCase):
         self.assertIsNone(ctx_dict['tenant_id'])
         self.assertIsNone(ctx_dict['auth_token'])
         self.assertTrue(ctx_dict['is_admin'])
+        self.assertIn('admin', ctx_dict['roles'])
         self.assertIsNotNone(ctx.session)
         self.assertNotIn('session', ctx_dict)
 
@@ -152,6 +153,7 @@ class TestNeutronContext(_base.BaseTestCase):
         self.assertIsNone(ctx_dict['user_id'])
         self.assertIsNone(ctx_dict['tenant_id'])
         self.assertIsNone(ctx_dict['auth_token'])
+        self.assertIn('admin', ctx_dict['roles'])
         self.assertFalse(hasattr(ctx, 'session'))
 
     def test_neutron_context_elevated_retains_request_id(self):