Cleanup req_format in test_api_v2_resource

Since XML support has been removed test cases in test_api_v2_resource
no longer need to specify req_format.

Change-Id: Ic6572abc3121535e19d21e9a34d70bb42b9782de
Related-Bug: #1380787
Merge "Cleanup req_format in test_api_v2_resource"