Fix arguments for method expected_success

In expected_success method we expect to get status code of
API response, but we use incorrect argument 'resp' instead
of 'resp.status' in several files.

Change-Id: I28f9e4862ddd42322757f5b206ddfb6ddabcfe0f
Closes-Bug: #1354389
diff --git a/tempest/services/compute/json/images_client.py b/tempest/services/compute/json/images_client.py
index 9877391..4af8331 100644
--- a/tempest/services/compute/json/images_client.py
+++ b/tempest/services/compute/json/images_client.py
@@ -76,7 +76,7 @@
     def get_image(self, image_id):
         """Returns the details of a single image."""
         resp, body = self.get("images/%s" % str(image_id))
-        self.expected_success(200, resp)
+        self.expected_success(200, resp.status)
         body = json.loads(body)
         self.validate_response(schema.get_image, resp, body)
         return resp, body['image']