Adds testcase to check CORS for token endpoints

[Kirishikesan]

Overview

This testcase checks whether the CORS valve integrated through [1] is working as expected through the following tests.

1. Adds CORS config to deployment.toml
2. Checks the CORS valve response by adding an allowed Origin header and a not allowed Origin header in the request
3. Response should have the Access-Control-Allow-Origin header and a status code of 200 if the request is allowed and a 403 status code if the request is not allowed through CORS.

[1] wso2/api-manager#1175

[chanikag]

Avoid import all