Remove FWaaS Noop driver as default and move to unit tests dir

Remove the FWaaS Noop driver as the default and raise an exception
when the fwaas_driver.ini file has an enabled flag without any
associated driver. This communicates a misconfiguration clearly.
The Noop driver is moved to unit tests where it is used.
Also some cleanups in related area.

Closes-Bug: #1250841

Change-Id: Ib6345923df05994ceffc0b1cbf265b53c23e97f1
Merge "Remove FWaaS Noop driver as default and move to unit tests dir"