Goal: 

As a developer, I want run all the nova CLI comamnds with native threading, so that nova will work post Eventlet.

At least the following CLIs are known to use concurrency:

• nova-manage
• nova-status

But the rest also need to be prepared to handle threading.

Acceptance Criteria:

• CLIs work in threading mode
• CLIs work in Eventlet mode
• CLIs uses the proper oslo.service backend based on the mode
• At least there are some jobs that uses nova-manage with threading mode.