Goal:
Create or configure Rally scenarios to test concurrent image upload operations in Glance without Eventlet.
For example:
  Image upload with concurrency `5`  and  each scenario test with different image size 1,5,10,15,20GB

Acceptance Criteria:

• Rally scenario uploads images successfully

• Multiple concurrent uploads are executed

• No upload failures or timeouts

• No eventlet related errors in Glance logs

To discuss:
Is this story should work reassigned to different team? Perf scale team?