Fix misuse of assertIsNone

Change-Id: I6f52e4dc7c7d0668ee2a401632cce51795a5aee2
Signed-off-by: Takashi Natsume <takanattie@gmail.com>
diff --git a/tempest/api/image/base.py b/tempest/api/image/base.py
index 0cc088a..c2f067c 100644
--- a/tempest/api/image/base.py
+++ b/tempest/api/image/base.py
@@ -177,8 +177,8 @@
         # If we added the location directly, the image goes straight
         # to active and no hashing is done
         self.assertEqual('active', image['status'])
-        self.assertIsNone(None, image['os_hash_algo'])
-        self.assertIsNone(None, image['os_hash_value'])
+        self.assertIsNone(image['os_hash_algo'])
+        self.assertIsNone(image['os_hash_value'])
 
         return image
 
@@ -201,8 +201,8 @@
 
         # The image should still be active and still have no hashes
         self.assertEqual('active', image['status'])
-        self.assertIsNone(None, image['os_hash_algo'])
-        self.assertIsNone(None, image['os_hash_value'])
+        self.assertIsNone(image['os_hash_algo'])
+        self.assertIsNone(image['os_hash_value'])
 
         # The direct_url should still match the first location
         if 'direct_url' in image: