Add XML support for test cases under identity admin.

So far test_service.py is not ready. Create_service, list_service and delete_service
in XML/admin_client.py are not working properly. It seems that Keystone does
not support XML for service API. A bug has been raised at
https://bugs.launchpad.net/keystone/+bug/1042144.
I have complied with the XML format as it described in
http://docs.rackspace.com/openstack-extensions/auth/OS-KSADM-admin-devguide/content/POST_addService_v2.0_OS-KSADM_services_Admin_API_Service_Developer_Operations-d1e1357.html

Change-Id: I60f72a0f99deff0bd8ee02bd2db5284d87481d5f
11 files changed