Moved VZ fixture into global pytest scope.
Removed the container-description spoofing in vz.

* It doesn't play very nicely with the way the VMFactory has to be
  tested. A sysadmin will have to provide a testing configuration file
  if they want to run tests on a production machine.
Implemented two vmfactory tests.

* There's some reliance on timing but nothing too terrible. I think
  that these tests will be maintainable as they're currently
  structured. I hope at least.