Run the Glance API tests to create and delete images during an upgrade
Logs will be written to /var/log/glance_rolling.log
The result of the tests is collected in Ansible, but the gate currently
does not pass or fail due to it - it's simply stored in the
'rolling_test_benchmark_results' variable and displayed.
Change-Id: Ie37c15fb3379f8b687e7e47e6aa45deb01802424