Update volume client check success

Updated all volume tests to remove the response checks
and move to respective clients.

Partially Implements blueprint: client-checks-success

Change-Id: Iff2cfa5dc531134d3c7938ff2eae09115ce763a1
diff --git a/tempest/api/volume/test_volumes_extend.py b/tempest/api/volume/test_volumes_extend.py
index 58bbe41..c9e80aa 100644
--- a/tempest/api/volume/test_volumes_extend.py
+++ b/tempest/api/volume/test_volumes_extend.py
@@ -33,11 +33,9 @@
         # Extend Volume Test.
         self.volume = self.create_volume()
         extend_size = int(self.volume['size']) + 1
-        resp, body = self.client.extend_volume(self.volume['id'], extend_size)
-        self.assertEqual(202, resp.status)
+        _, body = self.client.extend_volume(self.volume['id'], extend_size)
         self.client.wait_for_volume_status(self.volume['id'], 'available')
-        resp, volume = self.client.get_volume(self.volume['id'])
-        self.assertEqual(200, resp.status)
+        _, volume = self.client.get_volume(self.volume['id'])
         self.assertEqual(int(volume['size']), extend_size)