No exception is thrown when there is no class during delete API call

[Ashish Singh]

Currently, If there is no class in DB with a specified name then on Delete quota class API call, we get null. There has to be 404 object not found error. We should throw QuotaClassNotFound exception when there is no class with the specified name.

[Dimitri Mazmanov (sorantis)]

According to the REST API response guidelines, it is correct to send the 404 Not Found code in case an object doesn't exist.
http://i.stack.imgur.com/whhD1.png

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/439524
Committed: https://git.openstack.org/cgit/openstack/kingbird/commit/?id=fce80a3991195be7b0fe058d5fab5f4debe6752b
Submitter: Jenkins
Branch: master

commit fce80a3991195be7b0fe058d5fab5f4debe6752b
Author: Goutham Pratapa <email address hidden>
Date: Wed Mar 1 15:49:42 2017 +0530

    Fix issues related to delete quota-class

    Currently Kingbird doesnot raise any exception if there
    is no class in DB with the specified name.
    With this change we can fix this.
    Refactored some part of the code and added test-cases for the same.

    Closes-Bug: #1587363
    Change-Id: I0953c95459de31e223ec1ef658b76b3ab9d16ea8