Support quota hard_limit values of zero

Without this, the API fails with a 4xx error complaining
about an invalid field if the default cluster quota is
zero and you GET the quota for a project when the project
doesn't have an explicit quota set.  Furthermore, zero is
a meaningful value for an explicit quota.

Change-Id: I648bffab68e83f9573f852a12486f7ba11e4370b

Author: crawley

magnum/api/controllers/v1/quota.py

@@ -42,7 +42,7 @@ class Quota(base.APIBase):
     id = wsme.wsattr(wtypes.IntegerType(minimum=1))
     """unique id"""
 
-    hard_limit = wsme.wsattr(wtypes.IntegerType(minimum=1), default=1)
+    hard_limit = wsme.wsattr(wtypes.IntegerType(minimum=0), default=1)
     """The hard limit for total number of clusters. Default to 1 if not set"""
 
     project_id = wsme.wsattr(wtypes.StringType(min_length=1, max_length=255),

magnum/tests/unit/api/controllers/v1/test_quota.py

@@ -222,6 +222,17 @@ def test_create_quota(self, mock_keystone, mock_policy):
         self.assertEqual(201, response.status_int)
         self.assertEqual(quota_dict['project_id'], response.json['project_id'])
 
+    @mock.patch("magnum.common.policy.enforce")
+    @mock.patch.object(clients.OpenStackClients, 'keystone')
+    def test_create_zero_quota(self, mock_keystone, mock_policy):
+        mock_policy.return_value = True
+        quota_dict = apiutils.quota_post_data(hard_limit=0)
+        response = self.post_json('/quotas', quota_dict)
+        self.assertEqual('application/json', response.content_type)
+        self.assertEqual(201, response.status_int)
+        self.assertEqual(quota_dict['project_id'], response.json['project_id'])
+        self.assertEqual(quota_dict['hard_limit'], response.json['hard_limit'])
+
     @mock.patch.object(clients.OpenStackClients, 'keystone')
     def test_create_quota_project_id_not_found(self, mock_keystone):
         keystone = mock.MagicMock()