Fix parameter checking about quota update api

In quota_classes and quotas update API, parameters are checked
whether they are integer or not.
But when pass float values to these APIs, error doesn't occur.
Float values should be forbidden for the following reasons.
(1)If the value that user submitted and the value registered
   actually are different, user will be confused.
(2)Error messages of these APIs are "...must be integer...".
(3)In horizon, if a float is submitted, error message is displayed.

This patch fixes this problem.

Change-Id: I4c7df52ffff2d997da4e6267e25ec2ea4ab6f153
Closes-Bug: #1243037
Merge "Fix parameter checking about quota update api"