Change limits/quota clients to return one value and update tests

Partially implements: blueprint clients-return-one-value

Change-Id: Ib20882edb20b9b885d7fdca83d1dbd0180690f93
diff --git a/tempest/api/compute/admin/test_servers_negative.py b/tempest/api/compute/admin/test_servers_negative.py
index 2f0af72..bb04a4c 100644
--- a/tempest/api/compute/admin/test_servers_negative.py
+++ b/tempest/api/compute/admin/test_servers_negative.py
@@ -63,8 +63,7 @@
         self.useFixture(fixtures.LockFixture('compute_quotas'))
         flavor_name = data_utils.rand_name("flavor-")
         flavor_id = self._get_unused_flavor_id()
-        resp, quota_set = self.quotas_client.get_default_quota_set(
-            self.tenant_id)
+        quota_set = self.quotas_client.get_default_quota_set(self.tenant_id)
         ram = int(quota_set['ram']) + 1
         vcpus = 8
         disk = 10
@@ -86,8 +85,7 @@
         flavor_name = data_utils.rand_name("flavor-")
         flavor_id = self._get_unused_flavor_id()
         ram = 512
-        resp, quota_set = self.quotas_client.get_default_quota_set(
-            self.tenant_id)
+        quota_set = self.quotas_client.get_default_quota_set(self.tenant_id)
         vcpus = int(quota_set['cores']) + 1
         disk = 10
         resp, flavor_ref = self.flavors_client.create_flavor(flavor_name,