Remove redundant response schema check

All schema of compute action APIs are already implemented.
So we can remove the response schema check as the TODO said.

Change-Id: I473ef1a2916e2c772ee9497fe8d30e199d94669e
diff --git a/tempest/services/compute/json/servers_client.py b/tempest/services/compute/json/servers_client.py
index 1159a58..def799b 100644
--- a/tempest/services/compute/json/servers_client.py
+++ b/tempest/services/compute/json/servers_client.py
@@ -206,15 +206,7 @@
                                post_body)
         if response_key is not None:
             body = json.loads(body)
-            # Check for Schema as 'None' because if we do not have any server
-            # action schema implemented yet then they can pass 'None' to skip
-            # the validation.Once all server action has their schema
-            # implemented then, this check can be removed if every actions are
-            # supposed to validate their response.
-            # TODO(GMann): Remove the below 'if' check once all server actions
-            # schema are implemented.
-            if schema is not None:
-                self.validate_response(schema, resp, body)
+            self.validate_response(schema, resp, body)
             body = body[response_key]
         else:
             self.validate_response(schema, resp, body)